Bits

Bits are coins used as currency in Equestria in various episodes. They are small, round, gold-colored coins with an embossed rim. Filthy and Stinking Rich have the monetary symbols of cents and dollars as their cutie marks, respectively; Upper Crust and one of the paparazzi ponies in Green Isn't Your Color also have dollar signs as cutie marks. "Bit" is a colloquial term for certain coins, and also the term for the mouthpiece on a horse's bridle.

Depiction in the series
Applejack's recurring goal in the first season is to make enough bits to replace Granny's hip and fix the roof of her barn, which is why she wants to go to the Grand Galloping Gala with Twilight Sparkle in The Ticket Master, where she plans to sell her apple treats to make money. This is followed up in The Best Night Ever, but only one pony, Soarin', actually buys anything. In Call of the Cutie, while attempting to be a successful apple salespony, Apple Bloom first demands bits from a pony browsing the merchandise (asking for "cash or credit"), then puts apples in Bon Bon's bag without her permission and demands bits from her.

In The Last Roundup, Applejack offers her prize money from the rodeo in Canterlot to help fix the Ponyville town hall. The Mayor presses her about it before she leaves on the train.

In The Super Speedy Cider Squeezy 6000, ponies use bits to buy cider from the Apple family. In this episode cents are also mentioned as currency.

Pinkie Pie argues over the proper price of a tomato in Putting Your Hoof Down, and the price varies between one bit and two. Fluttershy negotiates over the price of a cherry in the same episode, and the price varies between 10 bits, 11 bits, 12 bits, and 20 bits, before finally being sold to Lemon Hearts for 2 bits.