I'm not familiar with Pico-8 at all so can't give you specific advice. But it seems popular enough based on the number of games here.
Everything you learn about making games is transferable but not necessarily the programming languages. You learn how to think about games from a player's perspective, how to do graphics, music, sounds and those skills don't depend on the programming language.
My advice would be to start with a game development engine that has good tutorials and work through the tutorials first. The tutorials should teach you a lot of the basics. Once you work through the tutorials you'll also get a feel for the software and whether you're going to enjoy using it. If you don't - move on. If you do - carry on making your own games.
Your choice of software doesn't matter if you're looking to maker small games with simple mechanics. It matters more if you're thinking of large multi-player games across several devices - because then you need to ensure the software supports all of that.