This will obviously take skill and patience to get. I tried several times and I got it using Jamaica. I used the default formation that Jamaica has a 4-2-3-1. I moved several players around.
You can change players but these where the ones that worked the best for me. Take advantage of their speed specially the attackers by doing one-two passes and chipped through balls. Using this formation nod players I managed to score 21 goals and only concede 6. The guy Raged on the final and I still got the achievement. Remember you need skill and patience, lots of it as I had tried several times before I got it.