There are a few main options for competitive Pretenders you can choose from. Scales builds, Bless builds, Expander builds, Specific Spell builds, and Rainbow builds. I would also like to add that these are the main things pretenders can provide and a good pretender will likely fall somewhere between/in several of these categories.
Full Scales builds are for nations (or players) that can expand well without needing an awake god that want long term economic value. MA Ulm, Ctis, etc. are primary examples of nations that really want nothing more than to max out their scales with an imprisoned pretender. The bless is minimal/irrelevant, the scales are glorious, and life is good as long as you don't develop a nasty case of elves. My favorite example of a full scales build would be a Shinuyama who took mostly scales on an imprisoned immobile, with just enough magic on their god for their sacred big mages get the Unaging bless (and maybe fire resist or MR boost or whatever. Depends on god chassis and if you have a specific forging goal or whatever for him).
The most standard version of a bless strategy would be a basic bless build. You have good sacreds- you want an incarnate skill or two, but don't want to full tank your scales. Maybe your elves could use lightning weapons or whatever. You do you. Here you might drop a few less important scales like temp and misfortune, possibly turmoil or sloth depending on what your nation needs. Often you get an awake immobile with most of their points put aside for magic, but it's also not unheard of for a nation with really good sacred units that can expand without a bless to take a dormant immobile with a mix of incarnate blesses and passive blesses so that around the time you want to start fighting non-indies your bless wakes up.
Congrats! You decided you don't want things like "growth," "money," or "research." That shit is for the weak! Your land may be a place of death and drain, but hot damn do your sacreds EAT EVERYTHING they come across. This is mostly done by Mictlan (whose dominion doesn't spread normally so the effects of taking bad scales can be minimized plus they have scary sacreds out of every fort), but any nation with overpowered sacreds could in theory try to hellbless. This style of play only works as long as you are eating other players, and tends to suffer the standard fate of absolutely wrecking their immediate neighbor then dying out as soon as other nations get enough magic to fend them off and simply bring more gold, mages, and research to the fight than the hellbless nation. Scary shit though, especially early on. Nations with domkill effects like Ermor and Lemuria sorta do this too. This is going to be an awake immobile god to maximize points for MOAR BLESS, unless you are even more crazy and go awake expander for an extra expansion party turn one.
Expanders are gods whose sole purpose in life is to single-handedly take provinces from turn one to guarantee a solid expansion (and deter people trying to continue their expansion into your lands). Almost exclusively monster chassis', they aim to be efficient at their task and save as many points for scales as they can. The great bulls, pigs, Drakon, really any chassis with earth can pretty reliably do this. Nations that are weak early and don't expand very well will often run expanders, for instance I am currently picturing arco. Terrible troops, god awful sacreds, really only want to survive until their communion setup can actually be relevant.
National Defenders are pretenders taken with the plan to turn them into an SC for your first war. This is often seen as a dormant titan with decent scales and a few magic paths. The goal is generally to have some magic buffs and construction researched for when they wake up in the second year. They then are able to be outfitted to deal with the early armies that your own troops are not able to handle at this stage. As noted, these are most often the titan chassis, as with just some preparation they can wade through armies. There is a consideration to be made as to whether more points should be put into scales or paths. The end result may look more like an expander, but with the extra points from being dormant, can justify better scales. At the same time, it is also possible to shift further into the bless should you have decent sacreds or into scales should the income be more necessary.
One of the main purposes of a god is to cast a specific spell. Maybe this is a global you really want, maybe it is a battlefield wipe your nation needs to be viable, maybe it is a strat you want to try out, etc. In this case you design your pretender to be able (with boosters) to cast this spell. Think the Wish spell, or perhaps you want to guarantee you can get Well of Misery or Mother Oak, or maybe the idea of a teleporting immortal god dropping Winds of Death sounds like a fun idea. Now of course this doesn't mean you ignore the bless/scales, it usually just means you pick a bless/scales build from above and tweak it just enough to be able to also do the spell you want. These gods will almost never be awake, so what will often happen is you have dormant or imprisoned god with passive bless abilities like fire/shock resist, strength boosts, blood surge, etc. then when he wakes up you drop the spell you have been prepping for and life is good.
Rainbows imply two things- first, that you have basically all the magic paths and second that you are awake to site search for said magic paths. While somewhat more viable now what with the dom5 bless mechanics, you tend to run into the issue that taking a crappy human HP pretender and then walking around slowly site searching with him is generally a pretty poor and risky use of a pretender. It would allow for an incarnate bless or two and some minor blesses, but it's tough to take the scales hit this would necessitate (remember the awake part?). Under no circumstances should you take this god dormant or imprisoned, by the times he wakes up he would be irrelevant.
Again, often a good god won't fall perfectly into one of these categories, but will actually embody two or more. Maybe your expander god with E/N paths picks up N5, so that the second you finish researching alteration 5 you can claim Mother Oak for yourself. Most common would be a cross between bless and scales builds. Do you want all the scales? Do you want an uber bless? Take an immobile imprisoned chassis, get a nice fat selection of minor blesses that are always active like stack a bunch of strength and stats and roll with that.