I would say it depends what you want to do the most, Piloting if you want to transport/fly around, Leadership if you going to build a lot and ComOp if you want to Prospect.
Can't say really, personally I loved to Prospect, but I'd look around commerce and ask factions what they pay the most for if thats what interests you.
Prospecting can earn you a lot of money, but it takes quite a while to do. It gets you a ton of XP compared to most other activities though. To be a good prospector, though, you need at least a 4 in comp ops--preferably 5, obviously.
I say do what you want. If all you want to do is get a job and crank out some boring stuff for a paycheck and play the monopoly-game, then sure, Comp Ops skill will land you the higher-paying gigs.
Piloting skill is useful if you'd rather be an interstellar truck-driver.
Leadership gives you a variety of production - spending all day in factories and shipyards or mines or construction projects.
I say, invest it in Ground Command and XP-hikes a bunch of NPCs as your personal army. Or invest in one of the arrest/execute-related skills and go do something dangerous! Or Dodge for the pure fun-factor roleplay thing!
This is a game, unlike real-life you don't need to get a corporate-style job to pay the rent and just be a big cog in the machine. Go crazy kid, use your imagination, invest in that Stealth skill!
Do what you want.
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"I like Justin Beiber Mash-Up's the best" is what I keep telling myself.