No such thing as a product that works for everyone, our hair properties and weather are so different. You can't easily DIY a proper conditioner, you would need to get hold of cationic surfactants and./ or fatty alcohols.
Ingredients that can penetrate or temporarily repair the hair include coconut oil, hydrolysed proteins and ceramides, you might look at Komaza Care products which utilise these and many are at pH 4.5 which is hairs 'happy place'.
2a-2c, medium texture, porous/ colour treated. Three years CG, growing out mechanical and chemical damage = breakage and very high porosity. Past armpit length heading for waist.
Treatments: Komaza protein, Komaza Matani, coconut oil with sugar syrup. Hairveda Sitrinillah
Leave in: Fructis Sleek & Shine (old), Gliss ultimate volume
Styler: Umberto Giannini jelly, Boots curl creme, Rockin RInglets
Experimenting with: Mega-Tek, Curl Harmony reviver, Elvive Full Restore 5.