Flex is the primary currency in the Grand Arena. With no resources of their own their currency is maintained from outside sources, procured by the Grand Arena from gambling profits. Gold or silver coins are pressed into a small cylinder nugget, this is how the Grand Arena standardizes different currencies from different realms. Fake coins are easily spotted while being pressed into flex, and flex also neutralizes the currency from any attachment to other worlds or governments.
Flex is for winners in the Arena, or visiting spectators. For all others the smallest currency is the humble Rose Petal. Thrown as prizes from the cheep seats, the few rose petals that make it down to the ring are coveted by those who have trouble maintaining wins in the arena. Used less as a currency and more as a tool to barter with those on the lowest class.
A primary way to exchange Rose Petals for various services is through a concierge like @Meryl "Derringer" Scope, although other bookies who serve @Grand Arena Book also can find things and offer services. "Derringer" Meryl has connections to all the inventors, crafters, healers, skin-traders, and spies in this continent. If the party/player has enough Rose Petals, Meryl can find what they want.
Food: Food can be found nearly anywhere within @The Grand Arena. The most basic rations being free, all you have to do is pull a ration out of the @Ration Dispenser. Ration Dispensers are located in nearly every venue that is not catering to the exclusive high-rollers. If you go to fancier places, they might have access to @Replicator which produces nearly any food you can think of, if you have the flex to pay for it.