Prep work

I like to build my own panels. To me this is part of my artistic process. I enjoy the physicality involved, the effort that has to be exerted. Often it is impossible to buy pre made canvases or panels that fit the desired dimension, anyway. I stretch canvas over some of my panels, especially the larger ones. Otherwise the painting become to fragile- large pieces of 1/4 birch plywood could break easily during transport. Breaking is less of a concern with smaller pieces In any case, one thing I don't like is painting on just stretched canvas. I do not like the large amount of bounce. Also, some of my paintings are close to 1/2 inch thick in certain areas and canvas only would not support the resulting weight very well.
I buy high quality gesso- it's more expensive initially, but, in the long run it saves money. You need lot less of it! Depending on the size of the piece there are different methods of applying gesso, usually I use a squeegee on large pieces and cheap wide brushes to edge and on the smaller pieces. I tend to use gessoing as a warm up prior to painting- meaning I facus on brush handling and movement while I prep. To me priming a canvas is much more than a necessity. It is action painting.