Gemtext ain’t very suitable for anything but text, I doubt you’d find any good resource with kind of content you’re looking for.
Gemtext ain’t suitable for complex text blocks as well, the best (and probably only) use of it is blogs. Lack of advanced text formatting, inline links, text blocks, tables, inline media and everything would make a wiki unbearable. Markdown would be much better for this kind of stuff, I wish solderpunk considered some limited subset of Markdown instead of Gemtext which is just way too simple. Although the protocol itself allows any kind of media, so nothing limits you from serving files with text/markdown MIME type. That would require a GUI Gemini browser with Markdown support though.