There is not a perfect answer, there will never be a perfect time to learn, you will never have all of the tools you need, and so on. Asking what tools.... I started with a torch, grinder, and stick welder. Far too often people see shops with every tool you can imagine and assume you need all of that to do great things. A great fabricator is someone who can think on the fly and make it happen with the resources presented. If you want to learn. Find something you want to do. DO it.... do it over and over until you get it right. Then move on to something else. I started before there was an interweb to read and watch videos. There is no excuse for someone not learning something with the access to information we have today. Learn something everyday. Never be outworked by others around you. I challenge myself daily to continue learning. I never assume the way I do something is the only or best way of doing it. I remain open to learn from who ever wants to teach me something.
So get started today. Start watching videos, reading books, talking to people, going to shops, offer to sweep just be around high level fabrication. I have a couple guys that come at night and work for free just for the knowledge they pick up here at the shop.