OP, I'd just like to throw out there that most of the information in this thread is only useful for 1 format or another, without really explaining anything.
The absolute first thing you need to do is choose your format. VGC is a bring 6, choose 4 doubles format. Smogon has a 6v6 singles format. Battlespot is a bring 6, choose 3 singles format. There are other formats, but these are the three that are the ones most played by a significant margin. Every single one of them has massively different teambuilding requirements, and knowledge from one format is near useless in the others.
You can experiment and figure out what you want to play the most. For example:
>>28725083>>28725292>>28725385These are posts aimed at the Smogon metagame. If you're not going for that, then none of the information they said is useful.
Smogon still has guides for VGC and Battlespot, and Nuggetbridge is a website devoted to VGC, so those are very good places to go if you want more information on those formats.