*sigh* - which preamp?

I would just use the search function and study past information, but I'm afraid on this topic that my understanding is so limited that I'd just get confused.

My turntable is an Audio Technica AT-LP120XUSB. My amp is a Yamaha R-N800A. Should I get a preamp? Which one? Should I upgrade my cartridge first?

Thanks. I'll go study some now so maybe I'll understand answers better.