I think a good first lens in your budget range (if the price of the camera was any indication) would be an older 150mm/5.6 Symmar convertible. You can find these for under $200 often. These are usually in decent Synchro-Compur shutters (if speeds are slow, figure around $80 for a CLA); they're single-coated and pretty sharp out to the edge of the image circle; and they convert to a 265mm/f:12 by removing the front element. The 265mm should be used stopped down at least to f:22 unless you want a particularly soft look, say for portraits.