Well .... my 2ps worth !
A lot of King Air's are operated single crew ... therefore you would need to have at least 700hrs+ (more like 1000) to get a job flying one, pref with a lot of multi experience. You maybe able to get a job as an assistant and build time on positioning legs, this may take quite a while ! ... As for the companies that do operate the aircraft multi crew you may have a chance especially if you KNOW someone, the turbine time will be an advantage, but will come at quite a price of paying for the type rating and trying to find a job ?
As for Instructing ... It is a great way of hour building and more importantly experience building, I learnt more from instructing and the course than most other flying courses .... A great experience that I wouldn't swap for anything, now in corporate aviation with a good background and a great knowledge of GA.
Firstly you need to get the CPL/IR etc out of the way and research the best options for you ... ! Do you want to go in to corporate aviation or the airlines (2 different worlds).
Good luck with the ATPL's and keep it in the back of the mind until your getting on with the flying !
EB
