This car will tell you how it wants you to shift. Listen to her and pay attention to your speed and RPMs. While the RJM pedal is a fantastic upgrade, it will not correct your incorrect clutch action. What it will do is make clutch modulation significantly easier.
If you're just cruising along you should drive it like a normal clutch. Accelerate to 3500 RPMS (or whatever you want). Clutch in. Shift to 2nd and allow RPMs to drop to about 2000 (or whatever is appropriate for your speed) before you let the clutch out. It will take dedicated practice - driving around hoping you get it right without paying attention to the vehicle isn't doing yourself or your Z any good. The car can be perfectly smooth when shifting properly.
If you're driving spiritedly and shifting at higher RPMs, the Z likes quick shifts. Accelerate to 5K+ RPMs. Clutch in. Shift. Clutch out. As quick as your feet and the car will let you
Note that this is much harder on your clutch than the above method.