All decent gimbals are £200+, it's not a simple thing to do and cheap ones show why. The Karma grip is worth the money IMO, purely as it controls the GoPro, I think a few others do too but not sure on Hero 5 integration.
None of these stabilisers will instantly give you good usable footage, they're an aid not a magic fix. You need to actually try, but they can be used well. Obviously none do up/down stabilisation, DJI do a Z-Axis add on that has half decent results though.
A6000 is a cracking camera, I used it professionally for video use for the last year until only this week upgrading to the A6500.
Always get proper mounts, it's just not worth the risk, they're cheap anyway.
Faster lens can work, Sigma do some decent APS-C primes, their 30mm is pretty nice...
Any of them will work fine, although FCP X runs quicker than both of them, as it's more optimised.
A quad core, 16GB of RAM and a dedicated GPU would all be on my wishlist (and things my current one has), so you'd be looking at a 15" as the rest are all integrated GPU only.
Downloaded it today, UI is much better from what I've played with, much needed catch up with Premiere Pro. Not sure why you'd need to spend money on training for it, pretty much everything is in the same place, icons haven't hugely changed etc.
From what I've seen as the Mavic has slowly got in the hands of reviewers, the Karma has no chance of matching it as a drone, for flying ability or image quality.
Karma really does look like it's designed for people who are deep in the ecosystem, more amateur stuff.
It's possible the delay is...