Like Vance said, the spring is set to fly with little or no pressure at some flying speed. The force you feel holding the stick in the neutral position will lessen as the blades come up to speed. The biggest difference in spring tension has to do with which blades you're using and how much gimble offset you have. Dragon Wings and Sport Rotors for instance, need much more spring tension than Bensen blades. The gimble offset, if reduced, will require less spring tension, but at the expense of reduced stability. The adjustment is usually done on the ground after feeling the sticks reaction in flight. Scott Essex makes a nice spring tensioner that can be adjusted in flight. Most 2 seat gyros have inflight adjustable trim.
Caution: If you are a new pilot, have someone more experienced fly your machine and help you adjust the springs. A gyro with springs substantially out of adjustment can be quite challenging and uncomfortable to fly. A brief hop into the air over the runway is enough to allow an experienced pilot to judge how far out of adjustment the springs are, and to take a first pass at dialing them in. It can take several little flights and small changes to get it just right.
The springs normally are set to pull the stick back against the seat when the rotor is stopped, but how HARD they pull is the key issue. Up-down movements of the mast clamp of a fraction of an inch will make a noticeable difference in stick pressure at a given airspeed. The "classic" goal for a Bensen is zero pressure (hands off) at, or just above, the best rate-of-climb speed -- typically 45-50 mph.