If I had to choose between the three I would make a case for the TCredits. At a cost of $36.25 for 125 TCredits gives you the needed 1500 VP. These TCredits are a form of currency at TripleClicks that can be used in a variety of ways. Each TCredit has a value of $.29 so they retain the same per dollar value. You can use them to buy products at your TripleClicks Store and bid in the Price Benders Penny Auction. You can even give them away as incentives and rewards.
