Don't power-level to try to race to new content, in fact it may behoove you to take in the scenery until 3.0 kicks in so that you don't have to FATE grind between lv47-50 (Quests 49 and under will give more experience to players once the expansion drops). On that note, you have to finish the story line quests in order to even access Heavensward content. Once you hit level 15 you'll be able to queue for Dungeons and you should be able to access Guildhests which are great sources of experience and puts you in situations where you'll learn the in and outs of group pulls and combat. You can access this and any other instanced "multiplayer" content through the Duty Finder which should be in your main menu.

I would also recommend that you join a new player friendly Free Company, which there should at least be a few who are ready and accommodating since the new expansion is hitting and there will be a flood of new & returning players. If you have a friend in real life who is playing then you should add them to your friend's list so you can shoot him questions when you need to.

Beware of RMT (Real Money Transaction) scammers, who will try to send tells, shouts, or yells trying to advertise something. Buying from them is not only against the Terms of Service, but it's a good way to get your personal information stolen.