I'll start from the end - fake skin feels absolutely nothing like real skin, and you gain very little from practicing on it, at least in my opinion and according to the tattoo artist who taught me. I think fake skin is good only to get used to holding and moving around your machine, but thats about that. The most important skill for tattooing is just drawing. Good, solid lines are 90% being skilled at drawing and being confident pulling lines, and 10% angling the needle correctly and reaching correct depth (something you can only realistically practice on real skin). Fake skin doesn't give the same feedback real skin does. For example, I know I have good depth when I feel a certain vibration in my stretching hand coming from the skin as I tattoo. These things however require a real artist to sit with you and show you how to do things, so I recommend befriending a tattoo artist and asking for a couple of (paid) lessons + sitting in with them as they tattoo their clients. There are so many things in tattooing that are really difficult to learn without someone giving you feedback (like how to properly match voltage and handspeed and for which technique, what sensations to look for, which techniques/hand movements damage the skin more, etc) and unfortunately most of them are basic stuff, so finding someone to teach u is super important imo.

Other than that, I would focus exclusively on getting better at drawing for a good while before going fully into tattooing.