I'm having trouble finding a bra that works for me?

I'm 21 years old, on a tight budget. I have a weird build so it's hard to find clothes in general, but mostly with bras. I'm a petite girl, but I'm busty, and depending on what brand/style the bra is I can usually deal with about a 36 DD, but usually it's still not a good fit...The bra rides up too high in back because of the weight in front, my boobs look lumpy because of the padding and my boobs pop out weird on top..And I can NEVER go without those things that hold your bra straps together in a racer-back style. Again I'm on a tight budget so places like Victorias Secret are not really an option. Basically bra shopping is a pain in the back (haha) and I'm just wondering if anyone has any non-expensive brands or stores that I may can find something that works. Or just bra shopping tips in general! Thanks in advance!