I barely never unlock turrets. I'm always glad to capture core turret controllers, I sometimes unlock MkI spider, on big exo games (golem/spire) I unlock full line of HBC, but on normal game I just build all MkI turrets. I spend my K on fleet and some starships, and a bit on economy (MkII harvesters, MkII eco comstat, MkII engineer) but almost never on turrets. I feel I need my K on ships to assault the core/home systems. I also play at low AIP (end up between 100 and 200).
The question is: how? How do you manage to spend K on advanced turrets (energy may or may not be an issue - ZPgen) and still have enough fleet power for the final assaults? Is this reliable only on 300+ AIP games with enough K to unlock both fleet and turrets?
I almost always unlock Mk III Military Command Stations, which allows me to get a LOT more mileage our of my turrets. So I unlock a few of the cheaper and more useful Mk IIs - Grav, Needler, Laser, Sniper - as needed, and rely on my mobile fleet and captured Core Turrets Controllers for the rest.
Basically, aside from minimal defensive unlocks, everything goes into Fleetship unlocks.
Of course, I also play with a very "disposable units" style of gameplay, where my fleetships are generally sent out with the expectation that they will die. Starships don't work in that playstyle, since they cost too much to replace, and you need a lot of fleetships (both types and Marks) to make a strong enough fleet. Mobile Space Docks help here, but I really don't have the Knowledge to unlock much else.