You'll need to set custom prices for anything in mods, but other than that it's pretty much good to go. The entity names for the coins are, from smallest to largest:
universalcoins:item.itemCoin universalcoins:item.itemSmallCoinStack universalcoins:item.itemLargeCoinStack universalcoins:item.itemSmallCoinBag universalcoins:item.itemLargeCoinBagYou can get a baseline for values from the defaults in config/universalcoins/minecraft.cfg and work from there.
I'd personally increase any minebay prices for items by 10-25% over what the universal trading station sells at, since you can order a first item from minebay without already having to have one in inventory, but that's just personal preference.
Thanks for introducing me to this mod, I'm definitely adding it to my modpack.