I like willow leaf designs.
http://www.willowleafstudio.com/ but really you can get pantos anywhere as the price per panto seems the same across the board. Just make sure you don't get one that is too large for your machine throat. Most of the sites that sell them indicate what size a row is and how many rows are on a sheet. with a 16" throat you are a bit limited for pantos.
It does get easier with practice. Very few new LA quilters hit the ground running on any aspect of LAQ. Just remember that the human eye is a remarkable bit of heavenly engineering. So if you stray off the line, don't try and go back and correct yourself, just keep on going and get back on the line as best you can as you travel. When you look at the quilting itself your eye wants to see the symmetry and unity of the design so it won't be noticeable to you or anyone else the places where you swung a little wide or strayed off as long as you don't make a jerky movement to get back on the line.
Personally, I worked from the machine from the front for the first couple of quilts before I attempted a panto. But some start off with pantos and then sadly never try working from the front of the machine.
Like anything practice does make you better. Not just longarming but drawing and doodling. Oh, one trick I was taught when I took my very first longarming lesson (so I could get certified to rent) was to trace the panto line with your finger at least once, preferably more than once, so you have an idea of the thread path and get a wee bit of muscle memory before doing it with the machine.