The guard is a notoriously difficult position to use in No Gi or MMA. 
Because of the lack of grips in No Gi, can be very easy for your opponent to open your guard and hard for you to attack them. 
However, there is an answer... it’s called the Williams Guard. 
The Williams Guard (named after Renzo Gracie black belt, Shawn Williams) is perfect for No Gi and MMA. 
It's relatively easy to set up, but also always you great control over your opponent and simple submission options. 
Oh, and it also works well in the Gi too.