welcome to the world of long arm quilting Lynda! you don't say if you already long arm (maybe on a rented machine) but my best 2 pieces of advice---be patient and practice--a lot. I was told to practice daily (which unfortunately I don't always take the time to do and it shows!) And secondly, load up a piece of inexpensive fabric and bat and plan on quilting it until it's covered with thread (a friend said to figure it's a picnic quilt and won't blow away!) use different weight threads so you get a feel for the way they handle.
Go ahead and purchase a couple of pantos--nothing wrong with pantos and it helps you get comfortable moving your machine with control (but remember that the panto lines don't have to be exact--relax). also get a couple of rulers--a straight edge and at least one that has a curve--you will add more as you go along and decide if you even like using rulers. I like Linda Taylor's straight edge one--fits my hand well, and DeLoa Jones boomerang, curved crosshatching rulers. But I love rulers and have many and am a sucker for more at shows, etc.
Speaking of shows--go to the biggies and invest in taking some long arm classes--I love them because I always learn something new. Opt for the classes that are at least classes that have you draw designs--the hands on classes are always more expensive, but if you can afford them, they are the best. also--take a maintenance class on your machine--long arm quilters learn to make lots of adjustments and maintenance that I'd drag my domestic machine to the repair shop. HQ has a good tech support--use it!
Most of us start by pinning our backs and tops (you will want to experiment with both loading the top completely and also floating the top--have the dealer show you both and discuss advantages of each), but you may want to move on to either using zippers or systems like Red Snappers for attaching the backs. But don't feel like you need to figure that out immediately--focus on getting comfortable loading your machine and quilting first. (I had to have my lap top with a YouTube video playing over and over for the first few months when loading my machine, now it's doable in my sleep)
Your dealer will probably tell you that ALL threads work great on your new machine--most of us find that certain threads just seem to be more problem-free--check with other owners of Avante's for best advice on that. For example, my Gammill doesn't seem to like YLI or Sulky thread for some weird reason--but loves #50 SoFine and Omni really well. Speaking of thread--download Superior Thread's free chart on their threads--even if you use another companies thread it serves as a good guide for similar thread type/weights showing the preferred needle size and type of use.
They also have a downloadable chart for bobbin tension for different threads. Other thread companies may provide the same--I mostly use Superior so don't know for sure.
Speaking of bobbins--I've found a Towa gauge invaluable--using it each time I wind a bobbin. Sure, I can judge bobbin tension dropping it into my hand, but the Towa is much more accurate and faster. Also--get your upper tension set and then adjust the bobbin tension as needed--that's right--bobbin tension is the one to adjust (I can hear my Mom shouting from her grave "Don't touch the bobbin tension!"--but that was a domestic machine!)
I usually buy 2 cones of the same color thread when I buy thread so that I can put one on the machine and one on my stand alone bobbin winder--makes things faster. I don't do this if it's a weird color or specialty thread that I'm not likely to use a lot. Buy your basic neutral color threads (white, creme, taupe, black, gray--and a sage green--that sage will blend with lots of things!)--you'll add more colors as you need.
not sure how much you currently mark your quilt projects on domestic machine, but do invest in some Pam Clarke (or similar) stencils that allow you to mark reference points. I didn't do this my first year and tried to basically not mark (worried that markings would not come out) and regret it. I use pounce chalk (white) with a foam brush for this purpose; water soluble blue marker and purple air erasable markers (less often because I'm still leery of them not disappearing) and my fav--F & P ceramic chalk marker and my Chaco chalk marker (but not the yellow!)
Look for and join a machine quilters guild--the one I belong to draws people from about 5 counties and only meets every other month, but I've learned a lot from the other ladies and that makes it worth it.
Lastly--don't compare yourself to others-I've come to realize we all develop our own "look" in LA just like any artist. I have a friend that is a master of feathers, another that does wonderful traditional custom work, another that does computer guided work that always looks perfect and another friend and I prefer more modern quilting. Focus on what YOU like best! And don't hesitate to ask the Board when those weird questions pop up! I've learned so much here.
P.S.--sorry this is so wordy!