Well, as someone with a technical and scientific background, I could carve out a niche for myself helping the residents of Gensokyo use outside world tech that happens to find its way in. The main problem is providing electricity, but I know how batteries and generators work. I think I could build such things if I had the materials. Of course, I would have to survive long enough to make it to a place of safety first. I'm moderately fit, but can't fight much and am not at home in the wilderness. But if I didn't become youkai food, I could go places.
After all, who can afford to buy (probably from Rinnousuke's shop) outside world items and hire a specialist (me) to teach them how to use and maintain them? Mostly rich people. Like Remilia. (Or Kaguya, but I doubt that the lunarians would much care for the "primitive" technology of Earth.) If I could get hired as Remilia's tech-minion at the Scarlet Devil Mansion, then I could meet Patchy. I could probably trade knowledge with Patchy for at least a little bit of magical knowledge. After all, she's expressed interest in things like "how does nuclear fusion work?" which I understand at least the basics of. She also has a lot of outside world books in her library that she likely lacks the knowledge context to make use of or properly understand.
Once I know some magic I can start doing more interesting things, like making some technology-assisting magics to help me out. To start with, simple stuff like making a magic-powered eternal battery or a spell to fuse broken circuit boards without heat or tools, but eventually I'd want to create something that would allow access to outside communication networks such as the internet and the cell phone system. It would not only make my life more enjoyable and convenient, but it would expand the range of services I could offer, thus making me more useful. And the more useful I become, the more wealth I can accumulate, the more knowledge/power I can get, the more interesting people I can meet, and the less likely I am to get eaten.
Fun stuff to do besides that basic plan:
1) Visit and talk to Sanae. As a fellow immigrant from the outside world, we'd have a lot in common and could enjoy each others' company. I'm not that interested in Sanae as MAI WAIFU but it's always good to have friends.
2) Get a pet and raise it from infancy. Take VERY good care of it and be very loving, so that it will live long enough to become a youkai and be well-disposed towards me. Who wouldn't want, say, a cute little nekomata of their very own?
3) Enroll in Keine's history class. The history of a place like Gensokyo must be very interesting, not to mention that many of the historical figures will be immortal or at least very long-lived and so will still be around. So it should double as a "who's who" of contemporary people.
