I have a group of friends who buy cotton sheets in the colour , fleece , charity shops or try online. I purchase large lengths 5yards of sale fabric . Not necessary the fabric for that quilt next one maybe. Also start to look at batting / wadding. This goes in between the top and back. Poly, cotton or mixtures look up a local shop. Come back or look up how to sandwich before you do it. It may be a good idea to make a cushion or a mat for a table to see how things work.
Don't forget come back here for any small thing somebody will have the knowledge to help.