Personally, I think the secret to Gleba is to get really good with the circuit network so you can do production on demand. If you're constantly burning huge stacks of spoilage, you're probably over producing. You should also try to lean your production toward long-lived items like raw fruits or bioflux and away from short-lived items like jelly or mash.

My Gleba base doesn't even have defenses other than a Spidertron I send to sweep the perimeter every few hours.

Rockets are very effective against Gleba enemies, as are Tesla turrets.