The main way to build you team to begin with is by purchasing card packs and hoping you get good players. Once you have filled your positions with quality players you will find yourself spending less time buying card packs and more time searching through the auctions for players you really need.
Coins
Do not spend coins on packs. There are cheaper ways to obtain players. Instead, save coins to spend on special offers in the Store or for bides at the Auction House.
Fourth Down
Always play the game as if you have four downs, it is not worth going for a field goal unless you are really close to the goal line.
Head-to-Head games
Decline challenges by players that are obviously pushing a stronger team. There will be no loss in fans by doing so, and the rewards for winning against a much stronger team is not worth the risk. Try to face opponents that are more evenly matched with your own team. Use the "Strategy" option to defend against specific plays that are being run against you. Because you are not in control of the defense in Head-to-Head games, take note of the plays that opponents like to run and make sure you have the most common ones in your active slots. When on a fourth down, go for the field goal if you are in range. Although unrealistic, scoring at every opportunity is the most important aspect in this mode.
Interception
It is vital that when you see the swipe command in the middle of the screen you try and swipe at the correct time so your defender gets a pass bonus and the chance of getting an interception.
Lineup
Do not rely on the "Best Lineup" option to always be accurate, especially with positions that require speed. Consider manually setting players in the WR, HB, KR and PR positions by looking at their Speed rating if all other attributes are somewhat the same.
Live Auctions
When you have assessed your team's strengths and weaknesses you may want to consider going to the 'Live Auctions' in the Marketplace to browse through the players that are available there and imporove your team. Make sure you don't spend a lot of coins on upgrading players by only five or six points, it's not worth it.
Plays
Do not follow the CPU's play suggestions, as its choices are very limited. After unlocking a decent amount of the playbook, call your own plays to ensure that you are using the best option for the current situation.
Set rewards
When you have a potentially unwanted player, check every Set to see if one has a spot for him. Completing a Set will result in useful rewards. If the player still cannot be used, use the Quick Sell option or auction them.
Smart trading
If you are looking for new cards and you'd rather not spend real money investing in card packs, take a look at the market. There, you can buy and sell cards at closer to their actual value. Be patient. Look around and buy a card that is going for a bit less than it probably should. Buy it and then list it, but at a price more in line with the stats (while still keeping it low enough to appeal to players). Keep repeating the process, making a bit of profit each time, and you can start to build up some reserves that allow you to invest in the more expensive cards that will build your team.
Tutorial Coins
Make sure when you do the Tutorial you poke around the different parts of the app as doing so will reward you with coins.