game is super shallow; in arena the most 'skill' is just drafting as well as you can. It's super addictive and fun regardless.
In arena you can play indefinitely if you average ~7 wins per, and with the daily quests that you can complete while in arena you honestly only have to average ~5 wins and that is definitely possible even with shit decks. Learn to draft; play arena, get decks. Also just about every draft guide / arena guide I have seen was shit so don't follow them.