How do i get extra rubies?

Answer from: Yazzo
You don't need rubies to meet the quests. That's just the game designers putting in a money maker

Answer from: Al
Upgrade or buy murchants to generate surplus gold, and then spend it on the mermaid. Try not to level up too often as this makes it less economically effective, because of exponential price increases of mermaid at each level.

Answer from: Brad Melb
In general you earn a ruby or two at each level upgrade you earn. You also sometimes get them for completing quests alternatively you can buy them using real money in game purchase.

As already stated rubies are really just the way the people who make the game make their money and there is very little need to use them in the game. The only real need for them is to complete some quests that require you to send mermaids to try find things. This in itself is like playing the porkies/slot machines where you generally loose rubies overall in an effort of gaining extra rubies, although if us required to complete some quests