I usually set science to the max out level.
There are a few times I might increase taxes if I know a couple of extra bucks might buy me that "special wonder" before somebody else... but science is the key to winning.
Money can be generated through trade routes, barbarian kings, tribute (if playing against an ai) Those marketplaces and other improvements really help. If you focus on trade arrows vs shields or food, money and science won't be a problem