Primer yes, especially using an acrylic paint....although Tamiya isn't really an acrylic, that is how it is advertised.

Primer gives your paint more to bite into rather than just the smooth plastic, as well if you are doing any resin, metal or PE work on the kit, primer gives you an even base to put your paint over.

For airbrushable primer, there isn't much better than the Vallejo line, (in one of 16 colors), for spray can primer you can't go wrong with Tamiya Fine Grey or White.