Hey! As far as problems go, yours is one that I wish I had.
Hehe.
For shopping, I would suggest that you try dept. stores like Kohl's, Dillard's, Macy's, etc. They tend to have nice women's sections, with lots of stuff in "regular" sizes. And at pretty reasonable prices, too... Personally, I like to go when there's a sale (Kohl's has the best ones!), but I have no idea what kind of budget you're working with, ha. Wal*Mart tends to have some nice clothes in the regular women's section, too, if you look hard enough! I do like Old Navy, and their stuff is pretty cheap, but a consequence of that is that it's also pretty cheaply made and tends to fall apart pretty easily. I would say it's a good place to buy something trendy that might go out of style soon, LOL, or if you're just buying some things for a transitional size during your weight loss, but not for stuff that you really want to last.
As far as the shopping itself... Er... What kind of style you have? I would say the best thing to do to start building an entirely new wardrobe would be to buy lots of "mix n' match" kind of pieces--stuff that can be worn in lots of different ways and many combinations, i.e. slacks, t-shirts, cardigans, tank tops, sweaters, etc in various colors. After you have a few basic pieces, then you should go for stuff with pretty prints or trims.
That's the best way to go for a classically put-together look, but of course, for all I know, you might be more of the type to go for a hot pink leopard-print mini-skirt, hehe! The best "advice" I could give would be to look around the stores that seem to go with your style, and if something catches your eye, try it on! If you find items that make you feel great when you wear them, go for it! OOOH, and if possible, bring a friend (one who's honest, but tactful, heh) who can give you an opinion on the stuff you try on... And maybe prod you into trying on things that you otherwise wouldn't.
Best of luck with the shopping!! If you can't tell, I LOVE clothes, hehe.
Hope you find lots of cute stuff.