Best AP bonus/cost
Adrenaline Shot gives: 20 x 3 = 60 AP for 3 rounds.
There are no stat requirements and the cost for Adrenaline is 300 (very cheap) which is almost free.
Second Best AP bonus/cost
Psycho-temporal Contraction gives the best AP bonus: 15 x 2 = 30 AP in 2 rounds.
Combined with Psycho-temporal Acceleration it gives: 20 x 3 = 60 AP in 3 rounds.
There are no stat requirements (WILL 3 is enough) but you will need 55 Temporal skill points.
Except -25% health from PSI pill, there are no additional costs because the PSI points are mostly free mana.
Worst AP bonus/cost
AGI 10. Blitz gives 20 AP for round 1.
AGI 13. Expert Sprint gives 10 AP for 2 rounds.
Lvl 25+. AGI 10. Blitz + Blitz specialization give 26 APs for round 1.
Lvl 25+. AGI 13. Blitz + Blitz specialization + Expert Sprint give 36 APs for round 1 and 10 APs for round 2.
This means that the maximum AP for one round is: 50 (base) + 20 (Adrenaline) + 22 (Psychotemporal Contraction/Acceleration/Specialization) + 26 (Blitz/Blitz specialization) + 10 (Expert Sprint) = 128 APs for the first round.
However:
Adrenaline + Blitz gives an user 90 APs for round 1, 70s AP for round 2 and 70s AP for round 3 for a total of 230 APs.
Adrenaline + Blitz + Expert Sprint gives an user 100 APs for round 1, 80 APs for round 2 and 70 APs for round 3 for a total of 250 APs.
Adrenaline + Psycho-temporal Contraction/Acceleration gives an user 90 APs for 3 rounds for a total of 270 APs.
Adrenaline + Psycho-temporal Contraction/Acceleration + Blitz gives an user 110 APs for round 1, 90 APs for round 2 and 90 APs for round 3 for a total of 290 APs.
Adrenaline + Psycho-temporal Contraction/Acceleration + Blitz + Expert Sprint gives an user 120 APs for round 1, 100 APs for round 2 and 90 APs for round 3 for a total of 310 APs.
Please tell me if my calculations are wrong because what I see is that Adrenaline + Psycho-temporal Contraction/Acceleration hits the sweet spot.
It also means that my super duper Sniper build is not-optimized.