I have fine wavy/curly hair that tends to frizz/flyaways (I've found this hair type pretty characteristic of Eastern Europeans especially...). I also have a pretty greasy scalp :( . I've tried minimizing shampoo use, co-washing, etc but it always just ends up so greasy it's just untenable for going out in public (and it makes me break out).
After some experimenting, I landed on Renpure brand "cleansing conditioner". It doesn't lather like shampoo, but gets off a bit more grease than regular conditioner; it's coconut oil based, I believe, but it doesn't smell much like it, which is a plus for bf who hates all things coconut. And it's $6-7/16oz bottle which yes, is pricey compared to $1 Suave but really good among "natural" products that are usually like $1+/oz. We haven't kept track too carefully but I'm pretty sure a bottle lasts us 2 mos at least (bf uses it too for similar hair, but shorter). I find <10c/day worth it to feel clean and pretty :)