I think we are all guilty of wanting to throw wanting to throw our plastic farther than we do.Who doesnt like to watch thier disc seem to defy gravity? But if you can throw your disc 300 and plant it where you want too why rush it? THE place to take strokes off your game is in the short game.Ive only been playing for two years, but have taken my game from a plus eighteen on a common round, to a standard -4 not thru huge gains in distance, but through the unexciting and unpopular honeing of consistancy. Think Maywheather in boxing. Very boring to watch, but very effective.your game as a whole is totally dependent on your short game...putting being the most important and underappreciated part of the game. Id rather be nut on from 60 ft than be one of the lucky few who regularly bang it 500 ft.( And yet in my dreams my game has both!) Good luck
Accurate D is the key. But as most have pointed out the gains are slow. One thing I tell all new club members is on casual rounds throw your putters and mids off the tee on the holes where its appropriate to do so even if its an extra practice shot. Someone who has great D doesn't think twice about throwing mids and putters into that three hundred range again depending on the hole. You may not be able to do that yet, but there is value in being able to throw mids and putters as proportionally far as you can without flipping them. The side benefit to working with the slower less stable stuff is that it cleans up you form, even if you don't notice anything really wrong with it throwing the other stuff. You will gain distance simply by learning to throw those putters and mids better. And it will help the short to intermediate game as well.
As far as discs that best suit you now, there have been some good suggestions. I'll add one I didn't see and thats the Gateway Assassin. Its a great disc, lots of glide, pretty nuetral stability wise. One nice thing about the Assassin is that after that disc came out two others built upon the same mold were released, The Apache and the Savage. One being slightly more stable the other slightly less stable than the Assassin. So you can kind of grow with that set. None of them are from the ultra fast category which makes them a little more foregiving of slight form issues and despite that they still go far, and I think fit nicely into the bag for someone hanging around the 300 to 400 area.