Congrats on taking the first steps towards a larger world of possibilities! Once you've gotten a little more comfortable, I would second having a go at making a vest/waistcoat. The first one I made was Simplicity 2346, variation 'D'. It's pretty straightforward and results in a nice garment (with the caveat that it doesn't have any darts for shaping... but that's what keeps it simple!) I shortened the main front and back pieces of the pattern by 3 inches, left off the patch pocket, and it made a very serviceable kilt-length waistcoat. I made one out of poly viscose tartan to match my kilt. I think the hardest part of the project was laying the front pieces out so the tartan lined up symmetrically; the actual sewing was a piece of cake!

And one thing to keep in mind, if you're looking ahead to making a traditional 8 yard kilt (for example using The Art of Kiltmaking as a guide): You'll be doing most if not all of the sewing by hand, so while the techniques and terminology learned from working other patterns will certainly be useful, you needn't be an expert at operating a sewing machine to make a fine kilt! I haven't tried machine-sewing a traditional 8-yard kilt yet, but knowing how much fabric there is to deal with and the precision required on narrow pleats, I could imagine it actually being harder to manage with a machine than by hand.

Happy sewing!

(P.S. Brewerpaul, may I inquire what pattern you used to make that gorgeous burgundy waistcoat?)