What do the terms "Landing Since New", FC, and FH mean on a Landing Gear RDAS?
Landing Since New - The definition is probably provided in Page 2 of the RAS.

This basically means the number of hours spent Landing from the time the aircraft was brand new . Based on this figure the blades will have to be removed. 

FH - Flight Hours - Basic unit for measuring length of time in service/before maintenance becomes due. The flight hour (FH) represents one hour of flight

FC - Flight Cycles - One Take Off and Landing