Myaghi

IMO you should pay the most attention to the head. Launch Angle, Spin Rate, Forgiveness... all basically influenced by the clubhead - not to forget Sound and Looks. Don´t get me wrong: I am not saying that shafts don´t matter. They`re very important when it comes to timing, feel, drip,...so to say can move / tighten the hitting zone on the clubface. But for me this is more "fine-tuning" and needs a pretty reliable swing (for sure flex and profile must not be completely wrong for one´s swing). I am sure, SIM is a great driver (haven´t hit it yet)... but so are many others. My reco is to not exclude them from the beginning. Go with whatever makes your bad hits less punishing, not your good shots better. PS: A Fitting is always a good idea in my opinion

Are your grips the right size? Thicker grips will help calming your hands down and, thus, cause less clubface rotation. Might be an additional help to the drills already requested.

Shafts atually do have less impact on spin as one would think. Clubhead and ball will cause significant changes (in case you play Pro V1x try ProV1 or even AVX). Besides what the others already wrote, you should also check your angle of attack. In case you are hitting down on the ball, your spinloft is far too high (which can be reduced by changing the loft...but with around 100 mph you should hit up on the ball 3-4 degrees [Trackman] anyway).