In order to get this, you need at least 3 cards from two different teams, or different attributes, etc. You can have 3 cards that are the same team AND the same chemistry, or mix & match, but you need to have 3 cards in each of two different attributes.
You will start with some cards, but you will likely need more from either packs or the Auction House. The best way to do this is to look at your Item Binder, and pick Team or Chemistry from the left side. This will pull up a list of each of the teams/chemistries and the number of each that you have. Then you can go to the Auction House and select a player for one that you have 2 in.
If you're looking to upgrade your team on the cheap, go to "More Packs." You'll notice that there are Silver Player Packs for 3200 coins, and Get A Player for 500 coins. Some quick tips:
-Silver Player Packs give you at least 1 65+ silver+, and 3 silver+ players.
-Get A Player gives you 1 silver+ player
-You can buy 6 Get A Player packs for less than 1 Silver Player Pack.
-For the mathematically challenged, that means you get 2 extra players.
-In the six packs I bought, I never got less than 65, and pulled a 73 gold.
As soon as you put the players in your lineup, this will pop.
Hope this helps!