I have been a longarm quilter for 7 years now and the learning curve was a lot steeper than I ever imagined it would be. Not only do you have to have the machine, which is quite the expensive investment but you must have the tools that go with it. The rulers, marking pens, pantographs, thread, wadding/batting, backings, stencils, preview paper, micro handles and plenty other tools that I won't bore you with, but just to give you an idea.
You need to be spending large volumes of money to be able to get wholesale accounts in Ireland so a lot of money goes into buying the tools you need to keep going. I know some longarm quilters are exclusively longarm quilters and some are longarm quilters that do some teaching. I am a longarm quilter that makes quilts to sell also.
I did a lot of my training in the US as I lived there for a few years but nowadays with Craftsy and iquilt.com, you don't need to be able to physically go to a class. Having said that I know most people enjoy going to a physical class, as there is the social aspect to this too. I personally love online classes because you have them all the time to refer to. I just need someone to give me a kick in the butt to make sure I do them all! I currently have a queue of online classes I have bought to do.
As well as classes, you really must have that hands-on practice and that can be expensive too as you are using wadding/batting and fabric for top and backing and all that thread too. I had the rare opportunity to be able to quilt for a charity in the US and got plenty of practice on quilts that would eventually be given to children in hospitals and sheltered accommodation etc. I took this responsibility seriously and put a lot of effort into those quilts and that effort paid off as I got the practice and am now a comfortable, less nervous longarm quilter.
Longarm quilting to me is an enhancement of a quilt and for that reason I choose threads that blend into the fabrics. You need to be careful not to blend in too much with your quilt top and forget about your quilt back, so choosing a backing colour like your quilting thread choice is probably something a lot of quilters don't really bother thinking of, but it is certainly worth considering.
I did a training retreat in Salt Lake City with Handi Quilter and we all brought in a quilt top to show to award winning quilter Suzanne Michelle Hyland and I would say that 70% of the quilt tops she looked at she suggested using monofilament thread. For those of you that don't know what monofilament thread is it is a see-through thread and Suzanne was suggesting it because if there is too much contrast between your thread and different parts of your quilt then it just won't look right and suggested using see through thread. I'm personally not the biggest fan of the monofilament look as I don't see anything wrong with seeing your quilting thread but traditionally your quilting thread should not be too obvious so as not to take away from the overall pieced quilt top.
There is so much to learn about in longarm quilting and each year they bring out more and more tools and rulers! We can't have them all but practicing as much as we can will keep the skill in check and in tune and progressing all the time.