Unfortunately the old rule "buy best glass and cheap body if you are on a budget" is not really true for digital.
Why? With film you could use a good film in that cheap body. With digital the camera incorporates your film (digital sensor and imaging processing). Still most digital SLRs are now good enough to show that lenses are poor.
That means lenses won't be cheap, but it also does not mean you need to buy the top glass. If you are on a tight budget stay with some excellent prime lenses.
Caution: changing lenses introduces dust
Uwe