^This.
I started out maining Ness because I also kind of wanted to be a low tier hero, but also he's a lot of fun... Until you just feel like you can't do what you want to do because of your character's limitations.
Now I know how the old saying goes, "A poor worker blames his tools," but when they're made of cardboard, maybe it's time to get some new tools.
That being said, it is cool to play the character that not a lot of people play, but don't overlook the kind of individuality that can come out of playstyle. Watching two different players playing fox is almost like watching two different characters altogether.
I'm not saying you shouldn't play who you want to play, I still keep Ness on the side for fun, but I've started to put more of my effort into characters that are going to output more visible improvement (Coincidentally, Falcon, Falco, and, albeit I don't play him as often, Marth), and I'm hoping that I'll see myself learning how to use the tools available to me to their greatest potential, and really knowing the game I'm playing instead of bringing a whole new dimension of a poor character and having to tailor my play to attempt to make up for his weaknesses.
Of course, there are exceptions out there, plenty of players have managed to make a name for themselves using a low tier character (Look up a G&W player named Qerb), but that's just the thing- They are exceptions. Not to mention there are players out there that are exceptionally good with low tiers, but primarily compete using high tiers (DJ Nintendo, for example, who occasionally uses Bowser). Now that's not to say that nobody else can be an exception, but it's a rough, rough, frustrating, and above all else, LONG road that might be more frustrating than fun to go down, and fun is a valuable resource.
In the end, play whoever you want to play, but know that it's a tough scene, and there's a reason we don't see a whole lot of low-tier mains competing at a high level.
BUT, tiers aside, my best advice to you as a new player (coming from a relatively new player playing competitively for about 1-2 years), have fun, know that this is a tough, but very friendly scene, the game is not very welcoming, but luckily the community is, exceptionally so. Make friends, get involved, and the learning and improvement will come as a byproduct.