The game is designed in such a way, that you can NOT make big mistakes before lvl 80, yet always make progress on something. So take your time, go an adventure, figure things out on your own. This extends to character creation, play whatever class, you want, all of them are good and have multiple, endgame viable, builds.

If unsure about anything, use the phenomenal wiki, ask IG or on the forums. ("/wiki" +[shiftclick an item] in IG chat opens the wiki site for the item)

The PvP lobby (crossed swords top left) has basic vendors, TP access and a bank. Use it to save afk, buy/store/sell things.

Do NOT use the lvl 80 boost on your first character.

As long as you and your friends are on the same Mega Server (EU or NA) you can play together, you have all race starter Waypoints unlocked.

Inventory management is one of the most important things in the game. Here is a rough prio list for loot:

1. Use the "Deposit All Materials" button top right in the inventory. You can access them from all Banks or Crafting stations.
2. Type "Consumable" into the search bar of the inventory, to find things you can consume (open all bags, consume all luck, karma etc)
3. Right clicking any item brings more options.
4. Identify or sell unidentified Gear on the TP. ->If you identify: salvage all white, blue and greens. For yellow and orange check TP value, if value is over 25 silver (2x Ectoplasm) sell, else salvage.
5. Selling to a npc vendor: use the "Sell Junk" button
6. Last possible option is to destroy things