i was waiting for a thread like this to come up…
in the last few galaxy events the recipes appeared to be much improved and required items that drop in combination from the same mission.
so far, one of the most efficient missions to farm is Stolen Honor on normal. it drops 6 items 5 of which are used in event recipes: Physiostimulator, Isolenear Rod, Phaser Type 1, EPI Capacitor and Basic Isolinear Chips. only 4 chrons per run, and pretty much every run is guaranteed to be of help in a galaxy event.
the second spot would have to go to Assault and Battery on normal. Text Book, Dermal Regenerator and Basic Earl Grey Tea. 4 chrons per run as well.
next, i would run Pillage and Plunder on normal whenever you need Basic Databases for a chance at some Combadges.
another great mission is Stolen Honor on elite. it drops Common ID Codes, Common Casings and Basic Clothing Patterns, all of which are used in event recipes. however, ID Codes are in high demand by any COM crew, i try to avoid any recipes that require them.
Beyond the Call on normal might also be a good choice if you need Translation Algorithms. Translation Algorithms have been excluded from the last three galaxy events(finally), but Basic Incenses and Basic Clothing Patterns are usually used in 2’s per recipe.
hope this helps, and don’t forget about Bone Knitting Lasers, Spectral Micrometers and Radiation Collectors.