Pinterest is your friend for this! Search “free-motion quilting for beginners”. You’ll find LOTS of inspiration, videos and tutes. Then doodle them out on paper until you get the rhythm down.Anything they do on a DSM you’ll be able to do on your longarm. Once I started doing this, I found I didn’t need any books. Save your money for thread!
A tip: when drawing them out, use your WHOLE ARM, not just your hand.