Training Courses Best rifle for starting training sessions?

Your post is somewhat ambiguous, are you asking if a 6.5 grendel is a good cartridge for a beginner and or if that particular bullet is a good choice? Almost any centerfire cartridge will do quite nicely at 200yds. A 6.5 grendel is a somewhat unusual choice for a 1st choice but is a very capable cartridge for what it is. What are your goals? What is "best" is a very subjective question without more information.
 
200 yards.......you can just close youre eyes and point to a rifle and itll work just fine......hell, even a .22 will do ya.

just get something cheap to shoot and youll be fine.