Pam’s suggestion is a good one. Gelli Arts have resources on their own web pages, you could try those (
here). Of course there are a gazillion videos on YouTube - your only difficulty there might be narrowing it down to ones that are interesting to you.
I think your best starting point might be to get yourself in the mindset that you’re just playing, don’t put pressure on yourself to start off with - just experiment, have some fun and see what happens. One of the beauties of gel printing is that you don’t have to use expensive materials. I don’t play with mine as often as I should but when I do, I usually use printer paper to pull my prints, not more costly cardstock.
Have fun!