haha, photography is an expensive hobby. Once you start, you can't stop. First, you'll be thinking that with a dslr camera, you can instantly get better photos, which is not true, coz you'll find so many aspects of photography to be interested in that require different equipment.
Firstly, you'll probably start with a dry cabinet to protect your new found investment.
Supposing you find out you like night photography, then you're going to have to invest in a good tripod and ballhead/panhead to get great shots.
Maybe you'll notice that the contrast that your current lens gives you isn't that great, then you can consider buying a polarising filter. After which, if you've done your homework, you'll learn that there are special filters which will help you get different effects, like taking a better sunrise/sunset, you might just decide to get those as well.
If you like architectural photography, then you gotta get a wide angle zoom or even a fisheye lens.
Then you discover CS has photoshoot outings with hot babes every weekend and you decide you want to pick up portraiture. Your kit lens will do, but you'll need an external flash, or you might even go into getting the diffusers, gel filters, reflectors, wireless sync cables, umbrellas, soft boxes, etc. (God save you if you decide to build your own home studio)
With all your new equipment, the small sling bag you used to carry is starting to look rather tight. So you start looking at Kata, Vanguard etc. bags to fit everything in.
Well.. that's a journey you'll have to take for yourself to understand. Have fun!