Garmin wrote the book on consumer level GPS units so I guess that's a good place to start.
I have a Standard Horizon unit that works just, barely OK. Mine has an external GPS antenna, and I'd recommend an external antenna for any GPS installation except the smallest boats.
I'd never recommend Standard Horizon, but others many have better experience with them.
Once you buy the GPS that suits you, pay attention to all those little wires hanging out of the back. Two of them can connect to your VHF radio and once connected (if you have an MMSI number) can signal your position automatically if you get into trouble.
Whatever brand you buy, good luck.
Bill