You guys need to differentiate "bad" and "difficult".
For example, jigglypuff is a relatively straight forward character, there are no advanced techniques or complicated set ups (rest setups dont count, they arent reliable). Her recovery is basic and she has no item play or trapping.
However, she is very very weak. So she is easy to use, but has very low potential and is difficult to win with.
For the sake of the OP, he should not even consider characters below top 35 for competitive purposes, regardless of how "easy" they are to use.
Id honestly recommend opting for an easy to use character who is also top/high tier. Easy characters allow you to gain proficiency faster, and good characters have high potential. Using a good character simply improves your chances of winning, which is the whole purpose of tournaments anyways.
Id recommend learning one of the following:
Mario, Diddy, Cloud, Mewtwo, Bayo, Sonic, or Marth. Theyre all relatively easy to learn and have the tools to do really well in tournaments (particularly when playing other top tier characters, which you will face very frequently)
One thing that hasn't been mentioned is to use the counterpick strategy. Learn multiple characters from top through mid tier and figure out which MUs you prefer each for, then opt for that char on a game by game basis. This is generally more effective in a Bo5 format and in top 8s but still useful in standard Bo3 or if you know your opponents char ahead of time. Dont let people know you counterpick though or theyll double-blind you before the match starts.
Also some people like to argue that low/bottom tiers can be a viable choice due to their novelty factor. But i generally disagree because novelty alone cant overcome the bad MUs all the bottom tiers face. If youre trying to take advantage of the novelty factor, you can still choose a high tier char as long as theyre uncommon in tournaments (ie: ryu, lucario, metaknight)