According to the muscletech website gakic is a pre-workout supp.. there is absolutely nothing in it that would interact with creatine.. take it before workouts, take ur creatine right after. You won't have a problem.
Personally I don't really trust muscletech and I haven't really read anyone posting on here saying that Gakic was effective or did anything for them... but you got a free bottle, it can't and won't hurt you, so give it a whirl.
It's got 100 cals/24gs of carbs so factor that into how many carbs u usually take in pre-workout, especially if you are cutting.