there are plenty of good legit no gi instructionals out there. You don't need a a gi, but it will take you longer to recieve the desired result without it. if you are determined to do without i would look up no gi experts like eddie bravo, eric paulson, pablo papavich, and marcelo garcia...they all have different approaches to the no gi game and different looks. I like to involve as many of them as I can together to get the desired outcome. that being said I also try to train with the gi at least 2x a week.