fuema

I'm new to SL and I tried looking up the answers to some of my questions but I couldn't understand them tbh and I've bought so many things and applicators to try and fix my issue. Also I apologize of this subject is in the wrong place. I read that only certain types of clothes work on certain avatars? Like mesh and layers. I bought a CATWA head and I know how to use everything head wise, but the clothes I buy don't look right on my avatars body. I'm using the classic avatar and her body is all box like compared to others on SL and I wondered if there is a way for me to fix it, like steps without having to change the skin I picked ( because the only body corrector I tried had mesh skin that came with it ) I want to know if there is a way to make the shape more round. And I noticed there are hands and feet to apply that some stores sell for more detail, would I need those too? I've even bought body types but they don't look right and I think I need something to edit the shape to make it smooth because no matter how much I edit my body shape it looks, off and noob like. I've link some pictures last picture is what I have in my inventory. Someone told me that the alpha files are to hide body parts ( they msg me this after seeing my atrocious avatar ) and I don't know how I'd use those, I don't want to hide all my body parts because that leaves nothing but a floating head. Also thank you, in advance, to everyone who replies in reply to my questions.