Is it Fulgora, because you've already got the infrastructure for dealing with belts full of semi-random junk?
Or maybe Vulcanus, because you can take all that stone you don't know what to do with and turn it into void flux and/or prismite?
Gleba, because why grow fruit when you can just conjure it out of nothingness?
Maybe Aquilo, because the place is lacking in basic resources so voidcraft comes in especially handy?
Or maybe just good old Nauvis, because you don't really even have to leave?

Space. So you don't have to bother with asteroid collection.

I made a flying brick that was fully reliant on Voidcraft to generate the fuel and ammo needed to go to Aquilo.

A little bit of everywhere, but all main production is on or above Nauvis. The other planets are mainly set up to produce the buildings that can only be made there. Gleba's base is teeny tiny because the only thing I need from it is biochambers. I've got a giant spaceborne factory that mostly stays above Nauvis and makes a bunch of stuff to drop down below, including carbon fiber and quantum processors. I never even bothered with trains because the tiny resource patches on my low-resource map aren't worth the trouble.

I like to voidcraft on shipyard (aka neumann V) that's the home of the nanites. thank you so much for this mod and all the work you put in it, it's super fun with all the puns. my spacecraft are all voidcraft, which sometimes had a probability of actually working sometimes in the early game. the void forge is really great in low power environments.