A lot depends on what your normal play habits are like. But, at 20 there are three basic builds you should have:
1) Cookie Cutter-
6/6/6/5/3 with every evolution in Explosion Damage, AE radius, and additional damage/force.
This is the build everyone expects you to have, mostly for the bubble and the explosions. You should pack the most damaging pistol that will not impact your cooldowns and it should be slotted with mele damage in one spot and a scope or armor pierce in the other. The pistol is mainly there to let you punch through centurian armor or target things down range, while giving your AE mele a burst for those moments when someone let trash wander too close. I recommend Pierce for the final evolution on Warp, because the boost to group damage and to detonations on armored targets far outlclasses the minor .3 second gain in cooldown. Paired with any other adept in the game, this girl is the wrecking ball of multiplayer.
2) Team Spec-
0/6/6/6/6 with the same evolutions as above and maxing fitness out for health and shields.
Basically, you are trading Stasis for a lot more HP/Shields under the assumtion that someone else on your team has either stasis, decoy, or turrets to contain phantoms. This setup is good if you are part of a regular team that includes an Asari VG or Salarian Engineer, because the only common need for Stasis is when facing Phantoms and those classes can deal with them much better. It also lets you pack a much better pistol, which is handy if you have not leveled up your Carnifex or want to bust out the Paladin. It can work in PUGs, but they might get upset that you don't have Stasis, so its important to let them know this before the Phantoms start showing up. If you never play against Cerb or are doing the FBW Gold Farm, this is the best build to use.
3) Adept/VG Support
6/0/6/6/6 Basically, like the above setup, but dumping warp instead.
This is a build you use specifically for teaming up with human VGs or Reave/Pull based biotics. Its also good if you are only facing Cerb constantly. This setup is best if your regular team includes a Justicar or Drell Adept, as it is just spamming throw on its own. It also works as a babysitter for a human VG, by dropping stasis on targets for them and mopping up leftovers with AE throw. Its a very specific situational build that you probably should not use in PUGs, as it needs specific team mates to get the most out of.
Of the three setups I like the second the best, but I ultimately respecced into the cookie cutter since I do so much PUGing and people expect the bubble.