Get a skein of medium-weight yarn in a light color (it's easier to see what you're doing) and whatever the recommend hook size it says on the label. Then watch some tutorials for basic stitches. I'd start making a little pot holder kinda thing with double or half-double crochet stitch. It's small enough that you can get used to turning rows, and it'll work up pretty fast with the medium weight yarn to give you some nice dopamine when you finish.

I would definitely recommended learning with just regular yarn, nothing fancy, until you get used to it. Yarn with lots of variability in the weight (as i expect plastic bags would have) is going to be difficult if you're not comfortable with the basics.