How much should i invest on dogecoin?

Many people have reasons why they should invest or not invest in a particular coin, however, I don't have a holistic answer to this question but I like to point to an inevitable saying in the cryptocurrency market and that is; Never invest what you cannot lose.
Secondly, I don't advice anybody to invest in dogecoin when he or she can earn it free through faucet like moondoge.io

Look for other coins and invest in either long term or long term, certainly not doge.