I'm doing a huge gigantice with the following abilities
Pacifist:
Soc +20
Influence +20
Speed +1
Influence +30
For some reason I'm the whipping boy of the galaxy this game, last crippling game I played I only had tribute demanded one time, this game multiple races are demanding tribute almost every other turn. I finally got ahold of diplomatic translators but so far they haven't helped. Also, in this game everyone is neutral or worse towards me.
I feel funny giving you advice since you got a 20k painful gigantic and I can't seem to hit 20k. . You might tell us what you are doing differently from that game that you played so well.
You might consider a little more diplomacy to start with but I agree with the speed pick on gigantic. Are you playing evil instead of good like you played before? That can change AI opponents' attitude toward you.
Sometime you just have one of those games when everyone capitulates to the strongest opponent who finds 3 rangers, gets the planet quality booster events, and has the best starting position. . Painful gigantic is hard for most of us.
For help on a painful game, there is the fantastic Unofficial Gal Civ Strategy guide by Gibbie99 and Relegh at Link