New Player
http://dulfy.net/category/gw2/
Plenty of guide for content, but also for guide on each professions.
http://metabattle.com/wiki/MetaBattle_Wiki
Here a site that regroup a lot of the most popular build for different game modes.
Best way to become a better player would be to practice. In PvE soloing dungeons and group content is probably the best way to be a better player, but since you are new start by doing by doing them in group. In WvW, to be a better player either you will roam and try to win outmanned fight or join a zerg bursting guild. In sPvP, well pratice and get better with different profession so you know how to play against each of them.
My best tip for new players:
1. Play the game and ask if you don’t understand something.
Even as somebody transition from another MMO, GW2 has a whole bunch of stuff that can’t be easily covered without being a wiki. Try out a profession/class, let us know what it is, and explore the world while the helpful people on this forum try to jam your head with information.