Goblin Mask - Complete your First Quest.
Slayer Bracelet - Reach Level 20.
Slayer T-Shirt - Clear the final dungeon in under 45 minutes with two or more players in your online party.
Best way to use your hotkeys
Use the RT section for your mana/hp and then the RB for your abilities. Or the other way around. This way, you won't have to waste time pushing buttons to use a move and you'll always have items ready for when you need it. Especially if you want to get a decent rank, cause the time keeps going even when the game is paused.