I haven't heard of the GFTN product you used but if you have fine hair the oils probably didn't help.

Second the Sallys idea. You can get a product called Neutral Protein filler (I think that's the name) and add a few drops to your rinse out conditioner.

Or you could just PM IAgirl here on the forum. She's my go to person for many questions!
Coarse texture, normal-high porosity, normal elasticity (Komaza Care), very weak waves
cleanser: Redken Fresh Curls Shampoo, CJ Daily Fix

rinse out: GVP Conditioning Balm, CJ Repair Me, CJ Smoothing

jellies/creams: CR Curl Maker, KCCC, UFD Curly Magic
gels: CJ CQ, BRHG