In addition to already excellent guide from TreysForDayys
there are 2 good resources I've used to get this achievement:
First, there are 2 tracks from Track Central created by user "A DELI MEAT" called Neverending Trials 1 and 2. Those tracks have very similar levels as in real Neverending Trials game, but you can return to last checkpoint/level as much as you like and practice. Obstacles aren't exactly the same as in skill game and not all of them are covered, but they were really helpful for me as I was able to get the feel of what I need to do and practice it. Just make sure you use all uppercase letters when searching the tracks by gamertag.
Second, there is a video I've found showing 110 rounds uploaded by TBNSoty which I've used a lot. It helped me understand proper technique used to pass the level. Actually I've used it so much that I've created web page with thumbnails of every level featured in video and linked it to correct position in video: https://sites.google.com/site/neverendingtrialsvideos/
BTW. I played around 70 hours of Neverending Trials before getting the achievement, so good luck and just keep at it.