Funny stuff but pretty pointless posting so far.
Lets get back to the subject. Fastest bud growth is dependant on the Strain, Nutrients and the Environment. Such a general question cannot be answered that easily. I love how people ask open ended question and expect detailed answers. My suggestion would be if you dont know what makes bud grow bigger/faster get a book and start reading.
Heres the basics anyway:
Co2, Optimal lighting , Proper NPK ratios, Optimal Temp/humidity all make bud grow faster.
NPK ratios and Nutrients you have to read alot to understand as they change throughout the veg and flowering cycles.
Co2 optimal level is 1500ppm (1200ppm supplemental and around 300 in the air)
Optimal Lighting is considered 3000-6000 lumens per square foot, some say 50 watts per square foot but watt dont make plants grow LUMENS DO
Veg temp/humidity 69-78 or so degrees and around 50-70 humidity
Flower temp/humidity 65-85(depends if you use Co2) 40-60% humidity.
I would suggest looking for a few books. I like Greg Hansen and Jorge Cervantes books the most but there are several others that have helped.