Unless you can find another mod that fixes some of the bugs (mainly main-story missions that refuse to end after being completed), than I would recommend Complete just to take care of those.
There may be something out there that fixes them without adding the other enhancements, but I haven't looked. I generally don't like how Complete throws gear and money around like candy, so if I decide to revisit ClearSky, I may look for an alternative.
As far as which game to play first, ShoC or CS, I think either way is fine. If you play ShoC first, you get the perspective of the core story before visiting The Zone before those events took place. If you play CS first, than it's just the opposite.......but either way will be fine.
ShoC is the far better game, no doubt. CS is certainly worth a play, though.....and I've probably gone through it at least a half dozen times.