Hair tips!?

So recently I've been having trouble with what to do with my hair to make it actually look nice. My hair is curly, but more wavy I suppose... I used to shower in the morning and then use a diffuser to make it curl. However, now I think it looks kind of ratty when I do that? Also, now I shower in the evening so if I diffuse it and go to bed it is super flat by morning. If I straighten my hair, it takes a long time to do and it's not long at all before it develops a few kinks and looks bad.. though I do like it straight. Are there any products I could use to make sure my hair stays very straight, or any other methods that could use on curly/wavy hair (I do plats/braids at the moment but I am not keen on the affect it gives my hair). Thanks :)