I am just about to get into competitive as well, tips are visiting smogon, looking for the pokemon you want to use, figure out how to IV breed and EV train. Also, figure out what natures you should use. All of your suggested IV and EV spreads along with suggested natures and movesets can be found on smogon. Try not to put pokemon out that will all have weaknesses to the same thing, you need to have divers typing so you can't be swept as easily.