You can upgrade a player's offense and defense by spending money. After reaching level 50 in either area you can begin upgrading the player's skills. There are six skills that can be improved. Spending money on upgrading a player's level is more useful, as it results in increases in points per tap (PPT) in offense or OPPS in defense. Start by upgrading each player's level. Ignore their stats until you unlock all the team players for your team and have them at a very high level. Then spend money to increase their stats. Invest upgrades in both defense and offense. Focus slightly more on defense because the penalties you can get for your opponent are higher than the PPS you get from upgrading your offense. However this may differ slightly based on the players you have signed. Upgrading your goalkeeper's player level in offense will result in a slight amount of PPS for each dollar spent instead of upgrading a field player. However, upgrading the goalkeeper in defense will give you better bonuses. Check your players to see which give you more PPS per level. To do this, get all of them to the same level and compare their stats. Concentrate on upgrading the best players first. Continually upgrade your striker, as he is the only player you will not be able to change.