I think that good, solid "neutrals" are important in any wardrobe. I'm a guy obviously, so things I think are a little easier and slack for me... I would say try to find a nice pair of darker jeans that fit you nicely and that you enjoy wearing. Darker jeans are easy to dress up with a jacket and a cute top, or they can just be dark jeans and a t-shirt, depending...
Usually black, brown, tweed, khaki, and of course jeans are considered neutrals... I'm sure there are a few others... Neutrals are things that go with just about anything color wise.
I would reserve the color "popping" for the tops, shoes, jewelry, etc... It is of course all up to you but shelling out more dough for something that will function as a staple in your wardrobe isn't necessarily a bad thing because you can do more with it.
This is all pretty much what Stacey and Clinton have to say. If you ever catch their show (the one that Mal mentioned) I think it would help out a lot. They have lots of useful advice and definitely aren't talking out of their asses... Tim Gunn is also good I've heard but I honestly don't pay as much attention to him (I don't get Bravo on my TV)....
Good luck and remember to remain positive and dress the body you have now.
-Sam