I'd actually recommend starting on TC, combat is significantly simpler without having to worry about the war or missile countermeasures (And enemy M8/M7Ms). Plus the plots are better.
AP does have more features and ships as well as being easier to set yourself up so the decision is up to you.
The X3 series does seem complicated but you don't really have to remember what every button does, I recommend memorizing the absolute basics before learning more buttons.
Before anything else, make sure to go into your keybindings and look for "Classic flight mode". I bound that to my r-click so I could switch to it at will. It's *much* easier to fly a ship using your mouse then your keyboard.
The basic buttons you'll really need are:
Accelerate/Decelerate: z/x
Strafe: w/a/s/d
Reduce speed to 0: Backspace
Max speed: Tab
Targeting system: t
Targeting system, object nearest to sight: T
Communicator/Allied ship command menu: c
Your command menu: C
Autopilot Dock/Enter Gate: D
Freight Menu: f
Pilot Menu: Escape
Fire ur lazors: Left-Click
Sector Map: .
Universe Map: ,
Speed up time (SETA): j
Message log: l
Cycle selected missile: m
Launch selected missile: l
Target info menu (When locked on): i
Select weapon group: 1,2,3,4
Other things like the property log, weapons menu, and mission log are accessible at the pilots menu, and the pilots menu also shows the shortcuts to reach those menus. Feel free to learn those at your leisure.