The Tri-tip is a great choice. I like it pretty thin. The setting I used on the batch in my video was even a little too thick for me. About 1/16-1/8” max on the cut. It will be about half as thick when its dry. I prefer having it cut with the grain for jerky myself. If tri-tip is not available or is over priced where you live you can also get a rump or arm roast if you can fine one with good marble in it and preferably the fat cap still on.