theres no such thing as a best formation that you wont have to change. basically every formation has its own weakness and there is a counter formation. i personally adjust my formation according to the team im playing against.

but if ur saying a good formation, i will use 4-4-2 flat or 4-5-1 v shape or 3-5-2 v shape. imo these are more balanced and by adjusting the arrows you can combat a lot of formations, but they do have their own lethal weaknesses.