I know someone said to diffuse right away to eliminate frizz but for me, that has the opposite effect.

I need to put in my product then let my hair air dry for at least 30 minutes (longer if possible) then I diffuse for like, 2 minutes, literally for some volume. I have to do this no matter what products I use or I get horrible frizz and no curl definition at all, yet I cannot skip the diffusing part of it or my hair is too flat on top.

Try that and see if doesn't help some, since I see that you tried diffusing right away and got a halo of frizz..

Good Luck!
HG's: (I alternate)
DEP Sport Gel, B&A Gel, Aura Naturalle Gel
(gel from mid-length down only, all used over a leave in)

Method: Air dry 20 minutes, then blow dry for volume.

2/3 mix waves/curls - coarse, frizz prone, med. thick, porous, at-home color for gray, protein sensitive but I still need it sometimes, glycerin-sensitive (I think) in high humidity, NOT CG but like stuff w/o silicones and that rinses out clean, wash with regular S&C 2x a week.