To get really great at free motion is really very simple.
Practice,practice and more practice.
Make yourself about 10 quilt sandwiches. That is layer 14 inch squares ( aproximate - I use my leftovers and scraps) of fabric, batting and backing and pin or sew them together on the edges. Then cover them completely with free motion. Number them from 1- 10 and by the time you do the 10th one you will see the improvement when you compare it to the first one.
This is what you can do after you have had some experience. Click on the pic to get more detail.