Depending on the network you wish to deploy your project on, you will need that network's native currency. For example, you will need ETH to use Ethereum, and BNB to use Binance Smart Chain. It is used to pay for transaction fees on the network, staking, and governance. Here are some ways to obtain them:
Purchase it on a centralized exchange like Binance, Coinbase, Huobi, Bitkub, or KuCoin and then transfer it to your Metamask wallet
If you've been on other networks such as Ethereum, BSC, or Fantom, you can bridge some tokens over with the Synapse Bridge.
When you bridge your assets over using Synapse, they will provide you with some tokens to pay for gas
You can then swap your bridged assets into your desired currency