It is 60 segments for gold, not 50, but you're most likely to qualify on miles rather than segments anyways.
Any trip you take on CO metal out of LAS is enough to get you the 1200 miles. I'd try looking on ITA and using the 300 mile radius option, specifying a few cities on the east-coast and see what you come up with for the cheapest fares.
Happy flying.
S.