GAMA is purely for the publishers, distributors, etc... it's also a good place to sell your freelancing talents.
Origins is GAMA part 2, but with the public invited. It is the second biggest Con Stateside (generally) and is a pretty good plce to make a showing and get back into the swing and ready for the MASS INSANITY that is...
GENCON INDY.
Where the fans eat each other to get at the latest mongoose release, climb over one another to buy product and hold sacrifices in the name of (insert rising star game designer here).
All in the first four minutes after the gates open.
THEN it starts to get fun!