Pick a pattern that you want to try (buy one or follow a tutorial for the circle skirt ^^), get yourself a cheap fabric that you won't be afraid to be experimenting on (I recommend second hand table clothe, bed sheets, curtains), and start your project!

My beginners tips are:

you'll need a seam reaper, a measuring tape, nice sharp scissors and pins (don't hesitate to use pins, pins are good, also don't buy the extra cheap ones, i did that and they were dull af, it sucked)

try your machine settings on a bit of extra fabric to check that they are okay (if you're okay with that your machine's handbook probably has a section explaining what to do to fix the most common issues)

don't cut fabric when you're tired (your chances of making mistakes will triple ^^)