How many keywords are good to use in meta keywords on a webpage?
Ankita: It’s been long Google declared that it doesn’t consider Meta Keywords tag for organic rankings. So, keywords meta tag is no more relevant.
You can add as many as possible but make sure they correlate or relevant to your contents .
As @pradeep said Google no loner use it as a factor for ranking but remember Google is not the only Search engine we are optimize for , so its not bad to make use of it . Since it won’t affect your Ranking negatively either .