This question depends on many factors that you have not clearly defined...
what engine are we referring to?
what kind of fuel management are you going to be running?
etc...
Chances are that this question has been tackled before for your application based upon their individual setup. Try the search button to see if you can find what you are looking for...I'm sure that with more info someone much more knowledgeable than myself will be able to give you a ballpark figure based on their actual experience and trial and error.
my friend has the MAM motor with a gt28rs and he runs like 24 lbs or somn like that. its like 15 daily and 24 at the track. purrty quick if i don't say so myself.