If your car has not been detailed in a while, claying is only going to do so much. A pre-wax cleaner such as Mothers Pre-Wax Cleaner (a non-abrasive chemical polish) is equally important since it removes oxidation and other surface defects (many water spots) that clay will not remove.
So I recommend: wash. clay. pre-wax cleaner (some call a polish), scratch remover, sealant/wax.