I have the same question but for the Oceanic Future, Virtual Future, and Space Age Mars, which units are best used in GBG in these three eras?
Based on my usage with attrition level,
Oceanic:
Initial - 6electric gel and 2subcruiser
Medium - 5subcru and 3 turturrets
High - 5subs and 3 glider, 8 subcrus, 8glider, 6glider and 2 Manta, 6nautilus and 2 glider
(instead of using any units from this era, future era hovertanks 8 units are much better to use in oceanic era)
Virtual:
Initial - samurai, monk, ninja (any combination)
Medium - ninja + ronin, rocket + ronin (6+2) or (8)
High - rocket + ronin (6+2 or 5+3)
Mars:
Initial - Tesla, sniper bot, marine (any combination)
Medium - 3champ + 5marine, 2 champ + 6tesla
High - sentinel (8), steel warden (8)
As a common rule, any attrition level picking units which can handle higher attrition is the best choice. Then why this confusing split because units gets varied with different opponents having higher attrition boost power. Initial and medium attrition level, didn't want to use my best units. Hence did the units splits in this way. It's not a good move but other units getting used somehow for battles and useful in a scenario of reserving best units for some quests to appear for battles.