there are panels that run about 12 dollars
https://www.ericas.com/quilting/tools/skillbuilder.htm

This is exactly what I have...great for practice! I paid $7 for the water soluble thread. If it turns out really good quiltE you'll at least know you can do it, lol!

When you get a little better (but still not confident about quilting a "good" quilt), practice on some panels and donate them to a kids' charity.

You can also draw on tissue paper then put that on the quilt to follow the lines. Tears out easily.

I made a bunch of placemats and practiced on that.

This was my thought too. Apparently, you hold the pencil still and move the paper as if it were fabric under a needle. I do know that my DIL "doodles" her designs for a long time on paper before she does her quilt. It makes sense, because your subconcious will record it and hopefully it will flow from your brain to your hands. Good luck.

Ann Petersen's craftsy class "Beyond Basic Machine Quilting" is an excellent way to learn FMQ. You make a small wall hanging while working your way thru.

Pencil and paper to start or a piece of thin Plexiglass and a wipe away marker. I think I saw that you tape the edges and then lay it on your quilt and practice......
see if you like the design

I make plenty of orphan blocks to pass time and/or just test color combinations.Later I assemble those to make blocks of about 12" or so. Having plenty of those I use them for FMQ practice. Later I can cut them to make insulation for potholders or for sturdier purse/tote bottoms. Nothing goes to waste here!