Yeah, it sorta needs a tutorial but at the same time its hard to say how one would be constructed.
Anyway, tips!
One the far right side of your skill bar will be where your Favor item goes. As you play game after game, you earn Favor. You then spend the Favor to unlock the Favor items. It then becomes free to equip, but you can only choose one per game. Once you equip that slot you cant change it until the next game.
RETREAT! The worst thing you can do in the game is die. It takes you out for a period of time and gives the enemy team tons of XP and gold. Don't be afraid to run away from a fight and heal.
Buy stuff. There are all sorts of handy items to buy, from healing potions, mana potions, teleport scrolls, and then other armor items like helms, armor, gloves, etc. Remember, the gold you have to spend is YOURS. You aren't splitting it between teammates so if you want to buy something, just buy it.
Teleport scrolls are a must. They can quickly get you back to home base to heal and buy stuff, and then can also get you back into the action just as fast. Buy them, use them.
While you have a limited number of armor slots, you can place anything into each slot. You can buy and wear 2 helms and 3 boots if you want! Each part is for a different ability. Boots usually are for speed, helms for mana, chest for health/armor, gloves for weapon damage, rings are misc stuff. Equip what you need, they make a huge difference.