A primer will definitely help your color coats adhere, especially the first coats you lay down, and especially if you use acrylics.

Enamels and lacquers are hot enough that they can adhere to unprimed surfaces (though perhaps not as well as primed surfaces).  Acrylics, generally, and especially water-based acrylics, don't bond to surfaces as well.  So it's a good idea to use one, if you use acrylics for your color coats.

I like Tamiya's Fine Surface Primer, but I also use automotive primers and Rustoleum.  Tamiya's primer is very finely-grained, while Rustoleum's and the automotive primers I've used are a little more coarsely-grained by comparison.  But they all work well. 

The only complaint I have with Rustoleum and the other brands is that I have gotten bad cans, whose vents clogged up-the hole in the top where the nozzle inserts.  That left me with half a can of paint in the can, that I could not get out.  That has never happened to me with Tamiya.  And for a small can, it goes a long way.

I'm sure others will have their preferences, too, both regarding priming, and which primer to use.  What I have written, is from my own experience. Your mileage may vary.