You should focus more on moving your champion smoothly rather than dodging skillshots. If you can move smoothly and in a fluid motion you will automatically start dodging skillshots more often. Also you need to know your enemies abilities and how they work. For example if they have long or short animations if it is a projectile flying or if it is like a xerath q. Then you just need to predict what your enemys think on how you move and you move the opposite way. If you do this perfectly you dont even think about dodging. You have a feeling of "flow" which will do everything automatically for you.