The gods in the Alpha were fairly straightforward. Time for a brief trip down nostalgia lane:
Best god is Pactmaker. Find him as early as possible (preferably at level 1), get his positively absurd 10 MP boost, and proceed to own. Glowing Guardian clocks in second; pick him right at the very end of the dungeon during the boss fight; you'll usually have enough piety to purchase a boon right away if you join late, so it ends up being two full heals.
If you're not into first strike or death protection then Jehora is a solid standby. You have to find him early, but he's easy to work with and offers great benefits. Also keep in mind that the Assassin "light foot" special technically doesn't count as first strike. Binlor is a little narrow, and mostly useful for the free ENDISWAL glyph to bust walls. He can also be useful for an auto-promote to level 10, which makes for an interesting gambit (particularly for Transmuters)
Dracul and Earthmother are both incredibly double-edged, but can be quite powerful if applied properly. Because Dracul bumps your level up, you'll lose out on bonus XP, and his health reduction on boon use can be difficult to manage, but he's got kickass powers at his disposal. Earthmother risks trapping you, but if you can set up a level 1 stoneform she makes the Pactmaker look like a chump.
Tikki Tooki is way too expensive to join by the time you've reached the late stages of DD. It will take you ages of scumming to rebuild your savings, so he's not even worth consideration. Taurog is difficult to work with and seldom worth the loss of your spellcasting power. Berserkers only. Mystera is universally loathed and by and large Assassins are the only ones who can manage having their attack power reduced to 1. However, if you're at the very end of the game and have already expended all your health potions you can join her to greatly boost your spellcasting power for your last push.
If you liked the alpha, you'll definitely enjoy the full version of the game. Hope to see you around in the future.