See section 2.2 of the FAQ
https://geminiprotocol.net/docs/faq-section-2.gmi
Thete are aggregators. For example
gemini://warmedal.se/~antenna/
or gemini://rawtext.club/~sloum/spacewalk.gmi
gemini://gemini.circumlunar.space/capcom/
or comnunity interest sites, like
gemini://tilde.green/ ,
which is in turn a site of
gemini://tildeverse.org
https://gemini.tildeverse.org/
Then there are systematic directories, like
gemini://medusae.space/
and search engines like
gemini://geminispace.info/
see section 2.2.3 of the above FAQ.