The currency of HPS is coins and gems. Coins are more common and buy most items, while Gems are more rare and are used to purchase gem-specific items. Both can be purchased with real money.
Coins can be earned by completing quests and games, visiting townies and friends, and sharing pictures. Any items purchased or gifted to you can be sold back to shop merchants for coins as well. Coins can also be found outside around town in the form of bugs, chicks, and balloons.
Gems are obtained when you level up. Sometimes, a townie you have chatted with will give you one gem.
Occasionally, a bug or chick will give a gem instead of a coin.