You require 3 Forma's without a riven, if you own a riven then you will need 4 Forma's

Instead of riven use [Drifting Contact].

If you like doing heavy attacks use [Amalgam Organ Shatter] instead.

You can also use [Condition Overload] instead of [Pressure Point] if you like I personally like [Pressure Point] more but use whichever mod you want, although with [Condition Overload] you get more damage in the long run.