If you are going for the premium designers, then I would suggest a Balenciaga city. It looks fun and young and it too has a good resale value if you decide move on to something else. It also fits a lot of stuff but does not look too bulky. The black fabric lining is easy to keep clean and the bag is very lightweight. The city bag has also been around a while and I do not think that it is going anywhere anytime soon, so it would be a good investment, one that you propably would want to wear later one too.
I do not know what age you are, but if you are really young, I would stay away from anything that looks too ladylike, because you have to be a certain age to pull those bags off without looking silly.