My car is metallic black...so you think a polish would be in order ?what colour is your car?
I'd recommend a polish and a clay, even though your car is only 3 months old, they usually come out the show room having been subjected to a very poor washing technique. The surface prep has a huge impact on the end finish.
Poorboy's Natty's blue is great stuff in terms of the finish, but would prob need applied every month as it's not the most durable