There is a lot of information on YouTube and the Top Eleven site. However, when building a team I followed these basic steps.

1. In real life soccer, what is the style of football you believe? In other words, how do you want to play.
2. Once you have your core strategy, identify which players you want considering skills you think matter, special abilities you like, and additional roles for flexibility against various opponent formations and strengths.
3. Develop a DAILY training program that suits your play style. This is a lot of trial and error as drill selection can have erratic effects on gameplay at times.
4. Start fine tuning and adjusting. Identify the opponent strategies that worked against you and develop answers to these play styles.
5. Continue fine tuning and adjusting as your environment keeps changing as well as your players.

In short, there is no best way. You need to develop your own philosophy and make it work with educated trial and error based on research and observations made on the field. Watching friends games can help give you a lot of ideas and inspirations.