Cap should be awakened first. The choice between the other two depends on your roster and needs. I have both at r4 awakened and use them constantly. Both amazing.
Is Warlock that amazing? I get his ability accuracy can shut down a lot of champs, but does the damaage get pretty good at higher tiers? I just pulled one today but have yet to rank him up.
I have Cap at 5/65 sig 200 and both Claire and Warlock at 6/2. I would definitely go for either Warlock or Claire. Claire is super sustainable and very suicide friendly. Warlock just shuts so many annoying things down. I typically bring warlock to AW and I always run Claire in AQ map 6.