I had one previous space-age run that stopped a bit into Gelba. If im honest I really didn't care for the spoilage mechanics. Finally getting to the point in current run that planet explorations on the horizon. Want to try something different. Please recommend me a good planet to try next without spoilers (or spoilage).
Fulgora first is what I did. It was hard without foreknowledge, just because of the terrain. No details, OP might be spoiled, but that was a heck of a challenge for someone who doesn't usually optimize for that particular issue.
Fun though, and then I had the science for power armor , which is a massive help in every world.
Anyway, OP, every planet makes each other planet easier. Gleba is centrally located, and while hard to automate, has as much iron and copper as you'll ever need. It also can produce everything needed for a rocket launch pretty easily, so its a good spot for a self-sufficient outpost.
The others each bring things to the table that make gleba easier, but gleba makes them easier too, so there's genuinely no wrong answer.
Fulgora is where I'd go if I wanted to kit up the engineer with the best equipment. Volcanus is where I'd go to kit up my factories. Gleba is where I go to kit up my science.