Starting boot camp.. What to wear?

I am very large (prob 20-22) and don't have any shorts or anything, so have to get something.. What do I need? I am in Brisbane and the mornings are generally very warm even without exercise..

Any suggestions on where to buy something suitable? Online ok if they have options for express postage.

I wear 3/4 length leggings (or sometimes yoga pants but these tend to fall down a bit) and a Kmart Tshirt from their plus size range. And a very good quality sports crop top (possibly Bella something?).

I get kmart shirts as they are cheap and my shirts tend to get stinky after a month or two or wearing while exercising so I chuck them and buy new ones. I did buy a plus size exercise top of special fabric but I bought it online and it is WAY too small.

I wouldn't wear shorts as they bunch up between my legs.