Design of pulse transformer
Step 1. Saturation. Calculate your worst case scenario voltage-time product, in your case peak voltage times max duty cycle divided by minimum frequency. Apply that to Vt=NAB. Adjust number of turns accordingly. This assumes you have already chosen a suitable core here. If not, you will at least know by now what area-turn product to look for. This sets your core size. 

Step 2. Does that number of turns even fit on the core with the wire thinkness needed to give low enough series resistance? If not, select a larger core and recompute for your new A. 

Step 3. Inductance and magnitization current. What are the limitations on your driver? Calculate Lprim by AlN^2. Calculate peak magnitization current by Ipk=UpkDmax/(Lprim,min*fmin). Can your driver support that? Great, you are probably done. If not, increase number of turns and or Al (different/larger core)

This should cover the basics for you. 

You will however need to consider many more issues with transformer driven gate drivers. 

How do you avoid staircase saturation? Do you run a capacitor in series? Do you have a reset winding? Do you limit the duty cycle?

How much droop can you accept due to leakage inductance?