I think the muslin is a great idea! Good for you for diving right in with dyeing fabric and choosing to make a quilt.
When I started, I hit the thrift shops for some fabric. Got a load of things like old sheets, big cotton shirts, jeans, flannel, tablecloths, and even some real fabric -- big load -- all for $25. I practiced on that. I did small projects, pot holders (which is where I came up with my now famous blue jeans potholders), lots of quilt blocks, some FMQ, figured out my thread tension, 1/4 inch seams, threading my machine and bobbin, worked up to a wall-sized quilt -- looked awful and wasn't square! -- practiced rotary cutting, precise cutting, got my rulers so they wouldn't slide, learned to use the same ruler for an entire project, read everything I could get my hands on, lived on this blog, and then I made my first quilt in over 25 years. No, not a newbie. Just real rusty. And the last machine I had was a "one stitch". These computerized models with a zillion options (all requiring a decision) took some getting used to. But at least I don't have to make my own button holes any more.
Best of luck to you!