The most balanced formation is the 4-4-2 classic.
Based upon the players you've got (assuming you haven't made any roster moves since your original post), either 4-2-2-2 hexagon or 4-3n-1-2 as your default formation. It depends upon which formation your players have the best form with.
If your able to watch your match, then playing the counter-formation game is an option as well.
Good Luck!