Learning to quilt nicely on your longarm will take just as much practice as it did to free motion on your domestic! It is a whole other skill set.
What really, really helped me was the wonderful series of instructional videos on YouTube by Michael Quilts. He does a great job of explaining how to approach the learning curve and build skills. Watching and following his methods was a breakthrough for me, and I loved his rulers as well:
https://www.youtube.com/channel/UCDc...YIewEeUtu7J__A
To get straight lines, ruler quilting is your best friend!