I've battled with this question for a long time and basically came to a non-scientific conclusion, that it has less to do with click volume than I originally thought.
Say you have two business owners. They both pay for the same keyword that gets 100 clicks over a one week period at a $1 CPC. They each pay $100.
Business owner A, gets 2 conversions at $300 aov yeilding $600 for a 5x ROMS (600 - 100)/100.
Business owner B gets 1 conversion at an aov of $150 for 50% ROMS (150 - 100)/100.
If the question is, how much data is statistically significant enough to take some sort of action, than Business owner A is most likely going to say "Raise my bid."(to what is a different question) While Business owner B will most likely, depending on his margins, say "Eh, lets wait and see, i don't feel there is enough data to say this keyword will, on average over time, perform at this level."
For keywords that don't get any conversions, I've historically gone with the rule that, if your site converts at 1%, then you need at least 100 clicks, and probably 300 to account for other friction/seasonality and unpredictable randomness that will never be known. But again, if the margin on just one widget is < $100, at a $1 CPC, you've already lost. But if your margin is $300, then keep running.