I am new to X Plane and have purchased the 777 as my first add on. I am sure its something to do with joystick calibration but the aircraft skews right or left straight away when full power is applied at take off. Its then difficult to control down the runway.

 

Any quick suggestions

I had this with other planes, mostly to the left.  In calibration there is a page to setup the centre of the joystick.  I found this was my issue.   You can also tweak the trims in the sim.  Think rudder is 5,6, and 7 on keyboard  (6 being centre).

How does a single engine aircraft perform?  Make sure that you don't have the throttle control/controls set to just engine 1 or 2 if you have a single throttle setup.  Use the setting (can't remember the terminology) that controls all engines or only the ones on one side or the other (depending on their number) will push you.  When I first started using X-Plane, I had a terrible time with stability, but they just "went away" after a while.  Don't give up.  It's great!

 

John