Where to buy my domains and emails?

We are just starting out our cold emailing process, we are a marketing agency. We are just setting up the process so still exploring on all the options. After researching online, i came up with 2 processes, Leave everything to instantly, buying domains, emails, letting instantly warm up and then start campaigns there.
Other way would be using a domain website like GoDaddy for domains, G suite for emails and then use instantly again for warmup and campaign.
Our scale would be fairly low for now, so was thinking about buying 1 domain and 3 email IDs.
Is there a better tool/process for me here?