If you are snatching up random colored bros and ccs and expecting to trade your way to the one you want, you are not going to be happy and are now sitting on a non-liquid investment.
You have to match up with people who then own what you want and don't have what you have.
I've bought, traded, swapped, etc for my keys, and I can say that only TWICE I've bought something for trade value out of the 20+ transactions.
Here's the criteria if you have yet to be swayed and still want to participate in this token economy:
1) Don't pay more than in your paypal (or wallet, or whatever) - Don't be in debt for something you want to flip. Bad juju
2) Don't pay more than it's worth - If you are buying a key to lock it down forever, you can spend a bit more on opportunity cost to avoid missing out. If you're wishy washy about wanting a key, you'd probably be happier with the cash in your pocket.
3) Know your **** - Mint gum and HOs don't become Mr. Fridays. Understand the food chain on clacks by reading through old threads, old classifieds, anything you can get your hands on.
4) Make friends - Trading works best if it's between two people who are friendly and want to continue to do business in the future. People will make more fair deals, and it will open up your network.
My 2c, take from it what you will. I'll just be waiting for the black skull that I swapped for this week