Most of what you called advanced tactics really isn't that advanced. Plenty of people use these tactics and aren't close to caring about competitive play. Regardless, I think what should be pointed out to you is that even though having fast reflexes will obviously help you out - playing smart will do you even better. Like learn how to power shield (if you don't know how already) and knowing to read someone's tactics. Like me. I'm easy to read with my Roy because he's a very straight forward character with a lot of hidden depth and most of his tactics rely on being able to actually go ape-**** on your opponent and getting in their face while setting up combos (which involve a lot of higher level tactics though). But, when I switch to characters like Samus, or Lucario my game plan changes entirely - not just because I am using someone entirely different but because the general idea, to using them is very different. And, like I implied earlier (or meant to) one of the biggest things you absolutely must know is the overall mechanics of your character - they're not necessarily hard to learn, but extremely essential.
--
Eh, but I'm mostly stating the obvious. Just approach higher level players and ask for advice.