So do I just do the story until whenever or what? Then go to pvp and what else? Sorry new to destiny. And what is the traveler?
First, if you want the lore:
watch (or rather, listen to) this video. It's long, but you can leave it playing in the background. The short form is that the Traveler is a mysterious Light entity that ushered in humanity's Golden Age (going from modern-day tech to rapid interplanetary travel and near-immortality). It was 'killed' in an epic battle, but it had enough Light to protect the Last City and usher in Guardians, i.e. you. No Traveler? No access to Light.
Absolutely finish the main campaign (The Red War) as soon as you can. You can participate in public events, and all that, but don't invest a huge amount of time in the Crucible or side stories. You'll know why when you complete it.
After that, it's mostly about boosting your Light level until you're ready to take on Nightfall strikes and the raid. You can do that by finding new gear and engrams, of course, but the best way to do that after the main story is to earn them from tokens and other materials that you can redeem with characters. Crucible, public events, loot caches, go nuts -- they'll all have something. One important tip: make sure you have the gear with the highest Light level equipped before you go to a character to redeem tokens, because the engram they'll offer is roughly as powerful as your current overall Light level.
There may be a point at which you hit a 'wall' for progress. If so, you can usually make some progress past it by doing Adventures (those orange side stories), strikes, daily goals, anything that reliably delivers engrams.
One final tip: some events you can't do alone, like Nightfall strikes or the raid (you can technically do Nightfalls by yourself, but it's very difficult). If you have friends playing D2, team up; alternately you can join a clan or take advantage of "guided games" that pair you with experienced players. And you'll probably want to have voice chat enabled for these events, since coordination can help a lot. Especially if you're new to a mission and need someone to point you in the right direction.
Yeah, this sounds a bit convoluted, but it's easier to digest when you're in-game.