Generally, level crafting last. There's no need to craft anything before you go to Depot A; once you get there, the only thing you'd really want is a suit of mutated dog leather or siphoner leather, plus perhaps some footwear. That only requires tailoring and a touch of chemistry. Once you get past Depot A and the world opens up, that's a good time to start making room for crafting. About that time, you should have nearly maxed out your world manipulation skills, like Persuasion/Mercantile/Lockpicking/Hacking, so you'll start to have room in your build to put points into crafting.
As far as how many points to invest, I still think destroyor's guide on steam is the best resource for that. If you're willing to see a few spoilers, the guide has all the answers you will want:
https://steamcommunity.com/sharedfiles/filedetails/?id=843557165Nobody can craft for you**, but you can buy everything you actually *need* to get through the game from merchants, so crafting is not necessary. It is, however, very useful and will make the game significantly easier for you. Since I know you're trying to fit some stealth in, you're really going to want Electronics so you can craft your own cloaking device.
I'll point out once again that you're asking questions that have been addressed in my psi guide. A few days from now, you'll want to start a post asking where to put your specialization points, and that's covered in the questions later on in the thread, too.
https://underrail.com/forums/index.php?topic=4149.0edit: ** technically, there is one NPC who can craft for you, but he only crafts one thing, and it's for a specialized purpose only.