How do i dress so my clothes fit nice and make my body seem flawless. i .....?

I am kinda medium weight and I always see people that are heavier dress so yhe clothes their wearing looks smooth. I just want to look like they do.when I wear clothes I have a muffin top and my thighs look HUGE also you can see every lump and imperfect part of me. I don't wear small sizes because I want to seem skinny. I know that would just make it worse. I also don't want to have to wear tummy control things all the time. Just tring to look netter for high school.