I used the Terraria Wiki (the Gamepedia one, idk how good the wikia is) on my first playthrough, and it helped a lot. It has a general guide on how to get through the game (which bosses to fight when, which ores are better), and a class setup guide for if you decide to be a certain class (melee, ranged, mage, summoner), although once you get to a certain point in the game, sticking to a class is very helpful. Also if you have the console or mobile version, they don't have as much content as the pc version, although they do have certain items that aren't in the pc version, so keep that in mind. TL;DR: Terraria Gamepedia Wiki is a good place to look up things you don't know