Hi Paul!
IMHO, the lenses for any camera should suit the type of photography that you are interested in. trhere are different lenses for different subjects at different distances.
If you can pick up a copy of Kodak's "Joy of Photography" at the library or bookstore, it would be an immense help to you. Thius volume will explain and demonstrate the uses of differnt focal length lenses and explain fast vs slow lenses and their uses.

Hi Ronk
Tks for your replied I will stop tonight by Barnes @ Nobles to pick up that book ,I dont want to make a mistake right away

I agree with Ronk's suggestion.
You might also try to get a sense of the range of focal lengths used by photographers you admire. For example, I like documentary/photojournalistic works of people in their environments, and the classic photographers tended towards moderate wide angle and "standard" lengths to some very mild telephotos; roughly 28-100mm equivalent, leaning towards the wider end. W. Eugene Smith carried 21-135mm (in the days before good zooms). I try to examine their works to see how they set them up. If you prefer sports or wildlife, you'll need longer focal lengths; landscape photographers tend to even wider angles than 21mm (equivalent).
The good news is that zooms are very good these days and it doesn't take many lenses to cover the bases. The bad news is that a lot of these zooms are slow (the F stop is fairly high); there are a lot of f/4.5-5.6 or so lenses out there. (For landscapes it doesn't usually matter.) So you might want to make sure that if you buy a zoom it will be fast enough for you. Even here there are tradeoffs because the very fast ones are not only expensive but heavy.

I think that learning more about the system through the books suggested is a great idea, but here's one that I got for my Digital Rebel XT and have been VERY pleased with it. It'll fit your 30D just like it was made for it:

EF 28-135mm f/3.5-5.6 IS USM

This is really sweet lens which now resides more-or-less permanently on the front of my camera.