So, you want to do something to really boost your level of play... and don't have any money? Well, no problem! There are a few ways to make your money last.
If you want to save a bunch of money (this takes ages, mind you) or you can borrow money from a family member, you should buy a booster box. It costs 80+ dollars, but for that, you get 36 boosters. 85/36=2.36; clearly cheap. You pay $2.36 cents for a booster. If you sell them all at store price, you make a win of almost sixty bucks-not bad at all. Even selling them for $3.00 (profit of $23) or $3.50 (profit of $41), you're going to be able to buy yourself a load of boosters back from your next box. And if you are school age and people at your school, especially beginners, are playing, you will sell out fast. The kiddies are astonished and happy to see that they can get four boosters from you for the same money that would've bought them three at the corner store.
Other options? If you are just starting, you might want to look around card shops. They usually have gigantic bins or folders of non-rare cards that go for 10¢-50¢. That is a great way to get off the ground if you are sure of your deckbuilding skills. At the same stores, you can also buy single rares (don't be creeped out if you have to give out 4$ for a card you need four times, that's actually rather cheap) to max out your possibilities. At the same stores, you can also find tournaments. While the constructed tournaments are something that the budget-challenged of us should stay away from, sometimes you can pick up non-rare cards from pros who just did a draft or sealed event-they will sometimes give you the cards they don't need.
Also, if you have any older friends who play magic, they often won't be hesitant to throw you a bone (be it a big rare creature they don't need or a gigantic box full of non-rares), especially if they are of the generous/not often playing type (Props to Arlo Farren, the person who gave me virtually every card I own).
I have seen all of these principles in action. They have all worked (and my friend Freddy still gets his cards by buying boxes and then selling all the boosters necessary to pay off the box and keeping the rest), some very well. Try it! You have virtually nothing to lose if you're still reading this sentence.
Power to the Poor.
-Budget Player Cadet