There use to be a lot of walkthru guides for Cosmos but for some reason the sites have become inactive…
However due to the Wayback Machine those guides can still be accessed. This one is pretty extensive and covers almost all of the Cosmos Agents.
http://web.archive.org/web/20160226001044/http://www.hb3.info/cosmos/
It’s written in German so a Translator will need to be used. CCP hasn’t changed those missions much so most of the info is still correct.
Here’s a written Gallente Cosmos Guide from the old Evelopedia for doing the agents in a specific order.
http://web.archive.org/web/20160225230341/https://wiki.eveonline.com/en/wiki/Gallente_COSMOS_Guide
Here’s a complete list of Cosmos Agents and their locations, also from the old Evelopedia.
http://web.archive.org/web/20160225230111/https://wiki.eveonline.com/en/wiki/COSMOS_constellation