My advice on AP, is if you have your targets lined up, and they're unlocked, keep pumping the AP.
Personally if I have say 3 openings, I'll have my 3 guys unlocked that I'm targeting, and I'll also have 2-3 more backups unlocked. At that point (especially if I'm leading), ALL of my AP go to my main targets. If I'm in a battle for one of them and not the others, he gets the vast majority.
It's common for me to have well over 1000 AP on a recruit at the time of signing. If you and an opposing coach are both "all-in" on a recruit, your 1200 AP to his 500 AP will make a big difference on the recruits choice, if all other areas are fairly equal.