Dominions is a complex game, and getting the hang of it will take many many games, especially if you strive to do well in multiplayer. In preparation for your first multiplayer game or in order to learn from your mistake take a look at this list of common beginner mistakes.
Naaira: This page is heavily opinionated so the origin of the opinion/advice will be noted for transparency. There is no advice that will fit all games (e.g. ALWAYS start fort building by turn 7, NEVER take drain scales), so use your own judgement and figure out what your game may be suffering from.
Taorec: One or less provinces are captured each turn in the first year ⇒ practice expansion several times in single player to get a feel for what your units can take with reasonable losses and hire mercenaries with spare gold. (also see “A Short Expansion Guide”)
Not-Lola: Always test expansion on a blank map (use the map for your particular game if possible with one AI opponent). Some nations do struggle with expansion and will get less, but aim for at least 20 when you test expansion in singleplayer. Some nations will struggle with this more than others and may have to accept less, is my general advice.
Not-Lola: Late Age expansion is a bit different. LA tends to be about getting enough armoured good troops to roll indie provinces because indie weapons are good enough that you can't just derp around with tiny groups or medium size poorly armoured guys, but once you GET those groups they tend to just keep rolling. so LA expansion (and some MA nations too) is about getting early res a lot of the time. This changes for some LA nations but the relatively tougher indies and higher rescosts on everything (and how little res capitals have) adds up to that.
Taorec: Expansion & wars are conducted only with large groups and only one or two provinces are conquered per turn, crippling economic growth ⇒ Split up armies so that many provinces are taken and losses are acceptable (trial & error) but combine them when necessary to get an overwhelming advantage (i.e. doom stack).
Taorec: Mages are brought when they can't cast any decisive spells (especially early on) and should be research or site search. In mid and late game they aren't committed in sufficient quantities when their spells are powerful and gem based spells win the battles ⇒ large mid / late game battles need dozens of mages and accompany them with sneaking scouts to ferry their gems.
Taorec: Armies & mages aren't scripted at all, thugs aren't scripted to attack and cast until they fatigue, the only commander is alone in the back and gets killed by fliers etc. ⇒ experiment with scripting, positioning and bodyguards
Taorec: Additional forts and temples are build late or not at all, hamstringing recruitment of troops, mages and research. Even worse is building temples in provinces with no castle, where opponents can easily raze the expensive structures ⇒ Build the first fort at turn ~7 before recruiting more expensive commanders, build temples in forts or if necessary as far from the front as possible
Naaira: Taorec gives a rule of thumb (fort construction started at turn 7) but it is important to note that a fort by turn 7 will not be possible for all nations. It is also possible to spend too much gold on infrastructure. Sometimes it is more important to get started on recruiting your slow to recruit mages in your capital rather than setting up a new fort.
Taorec: Units and commanders are recruited that are too costly or not useful against current threats, crippling expansion and wars ⇒ learn which units are appropriate to the situation (see nation guides here or on YouTube)
Gems are an important part of the game's economy. Gems enhance your magical power by allowing you to cast powerful spells, summon units, conduct rituals and create items. Here are some common pitfalls you might have slipped into when managing your gem economy.
cactusowl: You should not lose a war with gems in reserve if at all possible. Often midgame wars are won by whichever nation is best able to convert their early gem stockpile into efficient combat power.
Taorec: Gems are your life blood in later stages of the game, so start searching as soon as possible (Level 1 mages get ~60% L2 ~80-90% of magic sites while site searching spells double search speed at the cost of gems)
Taorec: Gems and mage turns are wasted by crafting unnecessary items (e.g. full equipment for normal commanders etc.) and summoning inefficient troops
Taorec: Knowing when and in which phase of the resolution movement and spells happen can be critical to winning or losing wars ⇒ learn when rituals, movement and sieges etc. are resolved in the Turn resolution sequence.
Naaira: For an overview of the Turn Order you can look at the Turn Order Sequence page or at this picture.
Taorec: Diplomacy is one of the most important (and neglected) factors in winning a multiplayer game. Unite other players against stronger opponents and divide them when leading the game.
A common rule is: “Your neighbor is your enemy, the neighbor of your neighbor is your (temporary) ally.”
Naaira: Read Toldi's guide to diplomacy. Check the diplomatic rules for the game you sign up for. Most games have rules that trades are binding but diplomacy is non-binding. Breaking a trade agreement will not be tolerated under such rules and the player will be forced to live up to the agreement by a gamemaster if discovered.
Breaking diplomatic agreements is not illegal but might lead to players taking action to punish the dealbreaker such as in-game coalitions or revenge in future games. In the end it is up to you to weigh up the short-term gain of breaking a non-aggression pact with the long-term negative repercussions.
To paraphrase Elyikiam: “If you engage in Game of Thrones diplomacy, expect Game of Thrones results.”
Figuring out your pretender design is one of the most important and hardest decisions to make, and unfortunately you will have to make that decision before joining a game. Maerlande has made a guide to pretender design that may help you on how to analyse your nation and make a decision. Taorec's All Nations Guide gives examples of pretender designs for different nations.
Causk: Usually people look at what would be good to have and try to fit it all into a build (take a rainbow elf nation build for example). By covering everything, you spread yourself thinner, because your economy gets weaker by every positive scale you skip. Sometimes its ok to leave points of weakness in a bless open and just speculate on snowballing enough to be able to cover that weakness in another way (for example snowballing via research). You see that sometimes too with people getting too many extra paths for variety, counting out how they could get every single magic path booster.
As a general rule it is better to do one thing well so you win your first war more convincingly instead of being mediocre at three things. While covering all bases in your pretender design might feel like the best way to secure the endgame, you need to make sure you get there. Also every point spent boosting paths is a point taken from boosting scales.
Causk: New players tend to underestimate the value of magic scales. Boosting magic can improve your research dramatically and can quickly give you a research advantage which will turn into a sizable advantage on the battlefield when you bring your mages to the frontline. Likewise, unless you have research mages that are unaffected by drain scales, drain can affect your research considerably over the course of a game.
Naaira: The value of luck is a hot subject in the Dominions community. While testing has shown that Luck is a great income scale over the course of a game (especially in combination with turmoil) it is also an unreliable source of income - you can't decide what you will be getting when.
cactusowl: Even more than gold, Luck is a source of free gems, particularly in non-national paths that you can't sitesearch for. If you take luck scales, be prepared to spend those gems on useful things; don't lose a war with gems in reserve.
Not-Lola: If you play the diplomatic game, i.e. control the pace of wars and peace such that you are never at war unless you want to be, the randomized income from luck scales is more helpful to you, as are greedy lategame-style strats. If you are invaded unreliably, then getting 1500 gold when you can't germinate a new fort due to raiding luck is less useful. Likewise getting gold on turn 29 versus a bit less gold reliably from turn 1 is fine if you just time all your wars so they happen when you're ready and can delay a turn or two if gold doesn't arrive in time, meanwhile if you're unpredictably at war or need to heavy mobilize to stop someone winning at the drop of a hat, reliable gold is more valuable.
cactusowl: Leaving a province with 0 PD is almost always a mistake. Someone else will capture it from you with a scout. Likewise, adding large amounts of PD to your provinces is only occasionally a good idea. Most player-built armies and many single thugs can kill unlimited unsupported PD; if they can kill 15 PD they can usually kill 25 or 30. But a PD dump can be useful when it is supported with friendly mages or heavy hitters in a defensive battle.
Causk: A common mistake is to produce too few scouts. This leads to too little information about the gamestate and thus missing out on opportunities, misjudging the relative strength of your opponents and being susceptible to misinformation from other players. If you have no native scouts be on the lookout for independent provinces that allow scout recruitment.
cactusowl: Scouts are useful for other things too: they haul gems around, build forts, ping enemy armies (attack and then retreat), ferry items…
Causk: New players have a tendency to play too passively. Sitting too passively, waiting for the next good thing, while someone else snowballs will rarely win you games. You always want to be thinking ahead to what your next war target will be - and who you will fight after you win your current war.
cactusowl: If you're staging an offensive war, be decisive and pull mages if they'll help you win. Yes, this risks your mages and slows down your research. But the faster you smash your opponent the fewer things you'll lose, the faster you'll gain income (which will let you pay for more mages), and the faster you can get them back in the lab. Likewise, if spending gems will ensure a fast victory, spend as many as you need.
Causk: Sometimes new players will continue to fight a war because of all the resources spent so far. But the worst thing that can happen to you is a status quo war, where neither side makes progress. In the mean time another player may be growing out of control and will be ready to eat you both once you have exhausted each other. Instead of focusing on all the money you have spent on the war it might be better to peace out and join forces versus whoever has had an easy first war.