Queen Michelle wrote a wonderful post on this subject the other day on Kingdom of Style. Make sure to check it out for excellent tips and things to consider.
Buying your first designer bag is an important moment, and the memory of it will stay with you much like a first kiss. Mine was a little black quilted Chanel purse, and I wore her until the day came to send her to a handbag farm upstate. I will never forget her.
Today, the handbag market is a bit different—especially now that the US dollar is weak, Parisian and Italian bags are respectively higher in cost for the American Glam Girl. Chances are you should budget around $1,000-$1,500 for your purchase.
My main suggestion would be that for your first (and perhaps for right now only) designer bag, you get one that has very classic lines, not an "IT" bag of the moment. You want a bag that will grow with you until you have the means to get another. You don't want to get a bag that in a few seasons someone can point to and say... "nice bag... circa Fall 2007, wasn't it?" You want a bag that would have looked just as good on the arm of Jackie Kennedy as it might on the arm of your granddaughter years from now.
I would make it black to maximize the number of outfits and situations you can wear it, and also because it will bear the minor scuffs and potential dirt best. Furthermore, should you consider reselling it a few seasons (or years) from now, black holds its value best. Similarly, I would choose from the Grand Old Design Houses — Chanel, Prada, Gucci, YSL, Fendi, Hermès, &c. While you may love a 2007 Michael Kors bag as much as a 2007 Prada, and they may have roughly the equivalent cost, which do you think will hold its value and resell better in 2010?
These are my suggestions for bags to consider as very viable candidates for a first designer bag:
Alternately, you may wish to start with a basic small shoulder bag like this little Fendi, and build from there once you have a firm idea of what you are looking for in a bag.
$357.99 (45% off) Fendi
Black Zucchino Small Shoulder Bag
Of course ultimately you should get a bag you absolutely love, never mind its color and shape. Just look around, do your research, and you'll know when just the right bag for you comes along.