Some advice on how to get better: Instead of trying to master Pit's moveset or looking for ways to mix up your attacks... Concentrate on punishing your opponent's mistakes. Force him into positions you want him to be in! A great way to do this as Pit is by camping, since they're forced to approach... Or simply weave in and out of their maximum range and force them to dish out an attack in the hopes that it'll hit you, where then you punish them for that (playing 'footsies').
You'll slowly get better at punishing the faster you react to things. And the faster you think on what to react with, the more fun Brawl will become for you! Learning about your character is essential, but on a larger scale, the fundamentals of what makes a 'great' player better than a 'good' player are still the same: reaction time, pattern recognition, thought processing or more specifically Analysis, finger dexterity, eye-hand coordination and experience. To get better at these things, all it takes is time... Personally, I would suggest using a fast character with lots of options (for me, it was ZSS), preferably of a very good tier level. If you can use that character at a good level of play, once you go back to your previous main you should notice a huge difference in how you handle situations (after I went back to Kirby, I was reacting to everything faster than ever due to how fast ZSS's movement and attacks are).
As long as you concentrate on those 6 aspects, I assure you that you'll become a WAY better player! I don't mean to sound egotistical, but before Pound4 I was considered a top player in PR. I haven't gone to a single tourament yet since then, but this saturday I will and am gonna win me some money! I've had a friend I've been helping become a good player (Lucario mainer), but no matter what I taught him about Lucario he just wouldn't get better, which gave me the idea that it wasn't his character dominance that was hindering him, but other individual traits.
I gave you a couple of links so you can read a small bit of what I mean. Hopefully it helps and changes the way you try to improve. Don't play to win if you want to learn, play to learn if you want to win! Hope that makes sense. :/