I would like to get an oracle for values of countries' based currencies. Are there such free oracles?
Chainlink's decentralized oracle network can easily facilitate this. You can either find your own data source or sources and make an Any-API request in your contract or depending on what data you want they already have a growing list of currency exchange rates in their list of data feeds. These are feeds that pull data from multiple high-quality sources, then have multiple oracles aggregate the data and post the final result on-chain, where it can be consumed by other smart contracts. More info in their Price Feeds docs