You will just gain them while playing like everyone else does. Of course they will make the characters stronger, but it will be no game breaker for you if you have none or only a few in the beginning. Just figure out which perks are essential for which class. Rough answer to that from this thread:
Rogues: Tainted Weapons (short: TW, needed to remove healing effects from enemies) and Finely Honed (short: FH, needed to remove shield buffs from the boss)
Soldiers: Resolve (used to remove “wreck effects” from yourself)
Healers: Steadfast Faith (short: SFF, needed to remove ruin effects from yourself and your group).
Mages: Unbinding Charm (short: UC, needed to remove root effects from yourself or another player)
Most fights require these perks but there are certain fights where you can avoid certain mechanics by doing extra stuff, in those cases the perks just make the fight easier and a lot more safe.
It is safe to say that pressing and decisive strikes are a first pick for every class.
After you have those essential AAs plus some more depending on the class everything else is just the icing on the cake. You will eventually fill up all of them, and you gain them passivly while playing. While it is annoying that you lost already gained points it is far from putting you behind whith no hope to ever catch up.