I am level 9, going to 10. I invest a small amount each season on buying tokens. As I said previously, I vary rarely use red packs for healing, and have NEVER power trained any player, or used a personal trainer. I have won several trophies, and am in tonight's CL final. I've also been promoted every season since I started playing. So as I said, with a full roster of players, injured players can be replaced in the team, and you can be successful, even without star players, sitting out through injuries.