Is it possible to sell your colony? Outside the archonexus plotline, I mean? I've done it once (the plotline, I mean), and that was enough. With my conservative play style, it's too tedious to do it all three times. If we're including endings, I've yet to host the High Stellarch.
As far as stuff, I've never used growth vats since I prefer quality colonists over quantity. For same reason, I've never used any of the slave stuff or most of the royalty clothing (robes, vests, crowns, etc.). I've not yet tried many of items from Anomaly, like the serums. The downsides just seem too large (which I understand is to offset the benefits, but still...).