My priority system, where the upper echelons overwrite lower eschelons.
(Important player goals are coloured brown)
P9 - ARS, Dyson, AI core worlds
P8 - Factory IV (perhaps blade spawner V, beam frigate V, etc.), Titantites and Adamantites.
P7 - most fabricators. Golems.
P6 - AI reductions.
(Important AI defenses are coloured green)
P5 - AI Eyes, super-fortresses, Black-hole generators (big road-blocks, do not enter without prep)
P4 - Raid engines, Fortresses covering ingress points, etc. (medium road-blocks, to tactically destroy, but not critical if entered accidentally)
P3 - Lone fortress, Ions of mark III or IV.
(Resource notables, coloured blue)
P2 - Planets with 6-8 m+c
P1 - Planets with 4-6 m+c
P0 - Planets with 0-3 m+c