Tips for those new to sewing
If there's somewhere nearby that you can take lessons, I'd recommend them. You can learn on your own however. I had one cushion making workshop where I basically learnt how to thread a sewing machine and sew in a straight line, and everything else I learnt from the internet.
There are loads of good beginner tutorials for circle skirts and gathered skirts online, they're a good place to start. I'd say make something you really want to make, but just buy double the amount of fabric in case your first try goes horribly wrong.
Some other general tips:
use a stretch stitch for stretch fabrics
make sure to use a uniform seam allowance
/r/sewing is a lovely community full of very helpful people
make a mock up of anything you're trying for the first time out of a cheap fabric
also take the time to make everything look nice on the inside. It will be worth it in the long run.
patterns are made for women with a B cup - there's a good chance you may need to do a bust adjustment if you use one
if you don't want to use a pattern, try copying an item of clothing that already fits you
if you get the sewing bug, say goodbye to all your money and time :'(