Chemistry
Try to get your players' Chemistry rating as high as possible so they will perform better. The Chemistry rating is displayed at the main squad screen and ranges from 0 to 99. It can be increased through the following methods. Play your players in their desired positions. If you have must use a player out of his position, try to make it as close a match as possible. The shoe icon on a player's card indicates their chemistry at their current position. Green is best, yellow is average, red is bad. Use players that match your preferred formation. Each player has a preferred position, usually matching the one they play in real life. The color of the small rectangle icon on a player's card indicates his happiness with the formation. Place players next to others from the same nation or club. The lines between players on the Squad screen indicates if they will be happy when linked with the players on the other end of the line. Try to have the line green by having both players from the same country or the same club. Use consumables to increase chemistry without having to exclude players. For example, you can change a player's position or modify a player's favored formation. This is why the same player may vary somewhat in Transfer Market.
Coins
You will earn experience points after each match. Level up to increase the amount of coins rewarded at the end of each match. A sizeable coin bonus is awarded for playing matches through to completion. Even if you are losing, complete the match.
Obtaining players
Purchase packs of players from the Shop using the coins earned from matches. You can also purchase them with FIFA Points, the game's premium currency. Complete the milestones listed on the "Accomplishments" screen. Most milestones will reward you with new players. Use the Transfer Market to see which players are being auctioned by other users. Either pay the "Buy Now" price to get the player immediately or place a bid, Use the Player Exchange to trade unwanted players or items for random rewards.
Various Tips and Tricks
Build a team with synergy between the players, so they will perform better together.
If you bring in a star but he doesn't work well with your other players, you're better off selling him..
When you complete a match, whether you win or lose, you'll receive virtual currency called FCC. This you can spend on Ultimate Team boosts, which can include a variety of benefits.
With proper boosts, you can earn an extra 1000 coins or so every 10 matches played in Ultimate Team.
Chemistry...