Everyone can benefit from sulphate free because sulphates damage skin and hair, ideally go anionic surfactant free. Consider their skin type as well as their hair properties not simply their wave pattern: certain oils and butters would be a disaster for those with seborrhoeic dermatitis (greasy dandruff) for example. Those with colour treated, porous or heat damaged hair should do well with ingredients like coconut oil, hydrolysed protein, ceramides and panthenol. Fine hair does well with protein, coarse hair does not.

Body Shop Rainforest Moisture shampoo and conditioner would work well for some. The Dermorganic line is pH appropriate for skin and hair and not specifically marketed to curlies. Like with commercial sulphate shampoos and silicone conditioners there is an element of trial and error to find products they love, maybe they could purchase say three shampoos and three conditioners between three people and share?
2a-2c, medium texture, porous/ colour treated. Three years CG. Past bra strap length heading for waist.

CO-wash: Inecto coconut/ Elvive Volume Collagen
Treatments: Komaza Care Matani, coconut/ sweet almond/ fractionated coconut oils, Hairveda Sitrinillah
Leave in: Fructis Sleek & Shine (old), Gliss Ultimate Volume, various Elvive
Styler: Umberto Giannini jelly, Au Naturale styling gelee
Flour sack towel, pixie diffuse or air dry.
Experimenting with: benign neglect