Get a ride to a tournament. When you go to college, go to one that's in Southern California(Bring the Wii!), there's plenty of competition there.
Try and actively think in your matches, try and predict your friends' every single move. If they roll a certainl way during situation X, then run to where they WILL be and hit them when they come out of it.
For the time being, when you play against your friends, do everything you possibly can to not get hit. If you're still losing at least one stock, try and not lose any at all. Once you can 3 stock them consistantly, give yourself a damage handicap.
Do everything you can to make it harder for you to win.
As well, pick up more characters. If you think Character X would be cool to use, use them. You're not in any tournies, you probably won't be anytime soon, you don't have much competition. If you can't evolve your abilities as a player, increase your technical knowledge. Use Mario for a single play session and no one else. Next time you play for awhile, use another character. When tournaments are available, go back to your mains. You may get rusty with them, but you'll always be able to get back to "where you were."
Or, to be more specified, learn everything you can about your character, and use all of their moves. When you grab(and shield grabbing is a very good tool) use Pummel to get extra damage, then throw. Use Tilts more, or that one Aerial attack that you just can't hit with.
You can still improve your game, you just need to be creative. Even all of these things will still mean you'll reach a peak where what you really need is a better player to kick you ***, but this should keep your busy in the meantime.