Well, this is my first essay about magic in a long time, so bare with me! But the question in the topic can be answered in one word: nothing. Stop acting like money is going to buy you professionalism, experience, and talent. Because it won't.
Every magician starts somewhere. Some start by picking up a mainstream magic book. Some start by picking up the 'LATEST STREET EFFECT!'. Some people see Blaine / Angel / Copperfield, and want to be just like them. Any of these ways is fine, but in the end, everyone must realize they will all start at the same place: the basics. Magic is based on the principle of making someone BELIEVE something happens, when it may not actually happen. If you can sell the idea that their card really jumped to the top of the deck, you're doing good.
So now, to get to the real point of this essay. Lately there have been a lot of topics about what to buy. These topics range from mature magicians who are looking for advice on a good book, to amateurs looking for 'where to spend da 20 bux!!!!'. Many people do not know the difference between need and want (as pointed out by Ben Lewis in a post of his).
I have Mark Wilson's Complete Course In Magic. There are literally 100s of effects and sleights in there. I spent months only learning from that book. Why? Because I just paid $10 for a 400+ page book. But in those months, I accumulated money from my job(s). Why didn't I buy the latest effect? Why didn't I buy the Instant Downloads I needed [sic]?
Those who have $10 and don't know what to get: stop fooling yourselves. I can tell you without knowing anything about you that you probably only know about 25% of the material you have access to. Stop saying that you have mastered all of Card College. Stop saying you have mastered ECT or RRTCM. If you had mastered ANY of these books, then you wouldn't be asking OTHER people what to buy with your money. Basic books like these will teach you what type of magic you will want to perform.
You do NOT need to buy magic every time you have the money. DVDs are good, books are a better deal. Last week, I went into a local B&M Magic Shop, and bought old manuscripts and books. Yes, books that were made before I, or even David Blaine, was born. From the 70s (some even from the 60s!). Do you know how much I paid? I paid $4 for a new copy of 'Entertaining With ESP'. And do you know how much information was in there? I was amazed at how many QUALITY effects and HELPFUL advice were packed into a book this size. Many of these tricks were being sold seperatly on DVDs or in '1 Trick' Manuscripts for MUCH more than $4.
Magic is meant to be practiced and perfected. Sure, I may be able to pick up Stars of Magic and learn one of the card tricks in an hour. Heck, I may even be able to go out and perform it for someone! It's a classic effect though, why not try and practice it some more? Perfect it? Find a way to fit it into my routine and work with my persona? I'd much rather spend a year learning the trick and then being able to do it flawlessly than learn it in a day and risk blowing it.
The point of this was to convince you to go back and look into all the magic you have access to. Books, little pocket tricks, DVDs, manuscripts, ANYTHING. I promsie that you will pick up some useful tips and tricks, and perhaps even a routine or two! If you need to ASK what to buy, then you don't have your past material mastered. And you may even save some money...