Collect cards for beginner deck
You can do a lot worse than the Deckbuilders toolkit for starting out, you will be surprised as well how quickly a collection can start to grow even just buying the odd booster or as said above taking part in local drafts or events. Your best bet for good advice about this would be at your local games store or even better at your local Friday Night Magic. They will welcome a new player and have lots of advice to give, tips, point you in the right direction etc.