I have a 4 finger/4 seam, curve, cutter and knuckle. Depending on the situation and whether we are playing 5 man will determine what pitches I throw and when. I won't throw many knuckle balls in a 5 man. If there is a cross wind, I throw more curves and cutters because it will move more with the wind. It's actually pretty crazy how far you can get a ball to curve with a crosswind. I only play Utrip and if there is one word of advice I can give to you, especially in Utrip, try and get a first pitch strike. That gives you much more leeway to get hitters to swing at what you want them to hit instead of what they want to hit. Also, move around on the rubber or in the "pitching" box. Give batters different looks and changing the speed of pitches helps a lot too. Best thing is just to experiment and find out what works for you.
As for grips, I grip my curve like a 2 seam fastball in baseball but put my thumb to the outside of the seam it runs along. You don't have to do all sorts of crazy stuff with your arm either. Just let it roll off and the way it rolls will cause it to curve. My knuckle I throw with all 4 fingers and just grip somewhere where the seams are not. Sometimes I'll put either my forefinger or pinky on a seam or put my fingers just under or just over a seam.