When buying any trading cards (i prefer yugioh) there are three components that the card/s must have the following:
1. Authenticity -- Read the item description to see if it mentions it if is genuine, if not there would be a good chance it would be a fake!
2. Condition -- This is more for a collector, but still should be a component. Make sure the card is in Mint or Near mint condition. This is good because one day you will lose interest these cards and if you would like to sell them, they should be in the best condition they can be!
3. Price -- The card must be a good price, again one day you will lose interest these cards and want to sell them and you would want to make a profit. A good website for Card prices is www.pojo.com!!