>>19663827Play VGC Doubles. It'll get you used to competitive play with a slightly limited pool of mons and introduce you to the concept of a metagame and how it can change over time.
If not VGC, at least play Doubles. There are a lot of moves in pokemon that literally do nothing in Singles, and the complexity of Doubles moves means you can do really well with your favourites as long as you play with skill. Things that are insanely broken or even very superior in Singles are less so in Doubles, same goes for things that are so bad as to be unusable in Singles.
Do what
>>19669123 says.
And play games. Play lots of fucking games. Don't spend hours wanking over lists or complaining about tiers like some do; get on Showdown and just play when you can. Battles in Doubles are typically 10-15 minutes at most, and every game is more experience for you.
Also have fun. Crush the weak and drive them before you, but certainly have fun doing it.
