How do I get more rubies?

Solution 1:

At the start of the game you are granted 20 rubies and forced to spend 5 as part of the tutorial. After that, you can gain more rubies from:

Leveling up - Each time you gain enough experience to level up you are given an award. Sometimes the award is rubies.
Tour gifts - Between certain cups you are given a tour gift. Rubies are sometimes contained in these gifts.
Rank-eligible cups - Some cups are "rank-eligible" and will grant you rubies for placing in the top spots.
Daily login bonuses - Rubies are awarded every few days.
Challenges - After clearing 7 cups you will unlock challenges which sometimes award rubies for completion.