1. buy domain 2. buy fastmail subscription 3. set domain nameservers at registrar to point to fastmail 4. setup domain on fastmail, setup email on fastmail,

1. buy domain 2. buy fastmail subscription 3. set domain nameservers at registrar to point to fastmail 4. setup domain on fastmail, setup email on fastmail, setup aliases (you need to pay for extra subscriptions to have separate mail users; i think same applies with gsuite).