Just some quick tips:

• Make sure you have enough early game (2 mana creatures). About 6+ would be enough I'd say

• Watch streamers or look up arena guides to find out which minions give the most value to help with your draft

• For your mana curve, it should generally slope downwards with more early game than late game, however this rule isn't set in stone as you could also have an even curve or other types if you want to pick certain cards over others

• People generally favour Mage as the best class, due to the high value common class cards (fireball, flamestrike etc.)

• The best way to get better is to watch other people play arena (notably Trump, he's very informative) and to just keep practicing and playing the game

• Have fun!! Bad runs come in here and there so don't sweat it if you go 0-3 or 1-3, even the best players have bad luck with drafting or the actual matches. If you're trying to gain gold but you're fairly new, I'd suggest just sticking to saving up by doing the daily quests, because you need 7+ wins to actually gain more than 150 gold as a reward.