You'll probably hear this a lot, but you ought to just try out many characters and see which one feels natural for you. As for easy-to-pick-up characters that's tournament-worthy, I guess you could try Donkey Kong. If you want one in the higher tiers, then Mr. Game & Watch wouldn't be bad to use, since his learning curve is pretty low, in my opinion: easy to use, but can **** very hard.
It all comes down to trial and error, as well as preference. That's pretty much all I can give in the way of advice. Also, you probably already know this, but you can go to the different character boards and learn more about each individual character there, and smashwiki can help to, by typing in the character's name, followed by "(SSBB)" in the search bar. Doing that will give you a great overview of the individual character and what they have to offer as strengths and how they suffer as weaknesses. Try it out. :3