Dollar Tree and stores like that are awesome. Everything is $1 and you can really stretch your money and get nail polish, makeup, brushes, nail file, women's deodorant, more feminine shampoo and body wash, socks and hosiery, general personal care products. It's really a great way to go.
And it's not great quality makeup, but it's not bad either. I've seen some ELF there. Also- walmart carries ELF brushes for a couple of bucks a piece for one to a few brushes in a package. And they are surprisingly high quality.
PLEASE don't get your makeup at a thrift store. Please. It's a great way to get pink eye and all sorts of other fun stuff.
My biggest advice- learning costs nothing. Download beauty apps, download voice training apps, check out videos on youtube. Read the girl's mags online- most of the important stuff is free on the site. While you are working on building up your money you can work on learning, and that will help you stretch your money further and make less mistakes.