Pick a relatively good deck, that has a good matchup spread. And learn it's matchups, mulligans and power plays for the deck. Consistency is all you need to hit legend. Once you understand matchups and understand the playstyle you like to play, you can start teching you deck to beating the pocket meta you are in. I wouldn't recommend playing multiple decks until you feel like you understand the meta and become very proficient at the decks you want to play. The biggest difference between legend and rank 5 players is the number of mistakes they make in a game.
Finally, take your time. You have an entire month to hit legend. Don't play on tilt and take breaks. Good luck.