It depends on the manufacturer of the rings but for an LS using OEM rings, the gaps should be as follows according to the service manual:

Top ring: .20-.30 mm
Second ring: .40-.55 mm
Oil Rings: .20-.45 mm

Even if they aren't OEM rings, that would probably be a good guideline to follow. Some engine rebuilders like their rings gapped to the smaller side of spec to obtain good static leakdown numbers. It is all up to you.