Native copper deposits would be green copper seams in exposed rock faces or red or green nuggets in streams or on the ground. I'm sure it wasn't easy, but it's how we historically started using copper. Having charcoal and learning how to produce a reducing fire or other methods of reduction allows you to smelt basic ores. After that, real chemistry kicks in.

The first step in changing a society is surviving. The second step is fitting in. The easiest way to do that without animosity is getting a job, and manual labor was a big thing 12000 years ago. No matter how good a carpenter you are, hauling around giant wooden beams isn't a one-man job. Likewise for hauling stones or bricks. Having done plenty of manual labor in my day, having someone who is eager to work and eager to learn usually makes it easier as an employer.

Gun powder can refer to black powder or smokeless powder (as well as some less common versions that were used for cannons and such). Black powder starts relatively easily, and is still reasonably stable. Good for flintlocks, but makes a mess of your barrel, so it requires more cleaning. The production of serpentine is basically grinding separate elements and stirring/grinding in the right ratios. It's very hard to ignite while making, unless you're reckless, but gets old relatively quickly. Corning will make grains of black powder, but the better methods can be quite risky. I don't imagine there were many amateur gun powder corn-makers. The process itself can ignite the powder if not done correctly.

Nitrate crystals will form in manure, bat guano, or urine. You would have to compete with the farmers for manure and the tanners for the urine, but if you have crystals you're close to the right thing.