Most of my side projects will never make money, so whenever I start them up, I want to keep costs as low as possible until I get some traction.
I went to my domain provider and looked to see if I could find a solution there. I use Hover, and they have a service that allows you to have a forward for $5 a year. They also have a $20 a year plan for small full-on mailbox setup: great numbers and an excellent solution.
I was looking at Fastmail and G Suite, and those both had similar costs of $5 a month.
Then, I found it! https://forwardemail.net/#/
Forward Email is an open-source email forwarding service. The instructions are pretty well set up on the site. But, you set up some MX records, and it will allow you to send and receive in your personal Gmail. This is a great simple way to get an address up and running quickly and they even have self-hosted documentation as well.
This is a great tool if you need to try out something quick, and once a side project gets traction, then you can move to a full-fledged provider.