Hello everyone. I’ve watched Bob Ross my whole life. I’m turning 51 now and want to give it a try. I’m looking at 18x24 double primed pre stretched canvases and have no idea which to buy? Some are 5 for $20 others are 5 for $60. Can someone tell me what I should be getting before spending any money? I don’t want to find out when trying that I’ve purchased the wrong thing, you know? Thanks in advance!