This is a warning and a suggestion!
Do the episodes from 25 or so first. Or 20 depending on your skill. But try to keep the first 15 for last or for when you expect to get an achievement for finishing X amount of episodes..
Reason is that each time you get one of the achievement for finishing X different episodes you wont get progress towards that last episode you did.
It is much better to replay the easy episodes than the tough ones.
So each time you are gonna get an achievement do one of the first episodes.Also after you beat any episode click to advance to the next episode. Then press start and exit game to the menu. But then wait 5 minutes (I always waited 6 minutes).
If you don't wait 5 minutes the game might not save your progress!