To buy GoodDollars on the Ethereum Mainnet, you will need to follow these steps:
First, you will need to have an Ethereum wallet that supports ERC-20 tokens. Some popular examples include MyEtherWallet and MetaMask.
Once you have your wallet set up, you will need to purchase Ethereum (ETH) on a cryptocurrency exchange such as Coinbase or Binance.
After you have purchased ETH, you will need to transfer it to your Ethereum wallet. GoodDollar's reserve is in cDai, so you can save some money in gas fees by also buying cDAI and avoid routing.
Then, open gooddapp.org and connect your wallet