1) My Lolita Dress- I have bought a petticoat, socks, and accessories from this website. It is a good site but shipping may be a little slow.
2) eBay- I bought accessories and 2nd hand dresses from here. I also bought 2nd hand brand on this site. It's a good site if you know what you are doing.
3) Bodyline- Most of my dresses come from here. I highly recommend this site for beginners.