The native currency of the Tezos blockchain is ꜩ (pronounced "tez"). You will find it on currency trackers with the symbol XTZ: https://www.coingecko.com/en/coins/tezos
On the site CoinGecko, you can navigate to the menu Exchanges and choose the Crypto Exchanges option.
From there you can see that there are multiple exchanges for converting other currencies to XTZ, including Coinbase Exchange and Bitfinex.
Regulations vary across geographical jurisdictions, so you will need to find an exchange that is available in your specific location. In New York for instance, Gemini is one of the only places to purchase XTZ: https://www.gemini.com/
Learn more about the Tezos blockchain here.