Cheap boxes are cheap nowadays. It really depends on your risk tolerance and skillset. If you have the skills, then lowendbox.com (or hetzner) is your friend.
You most likely will never outgrow your first box, because you probably won't have m/any customers.
That said, if you want to scale w/o work cloud is really the way to go. Our infrastructure costs are less now with 1bn requests (250TB) over 30 days compared to when we were doing 1k requests/month. That's what can happen when you leverage the cloud. And that's with 2 mostly FTEs. That even includes the massive amount of telemetry we have (which we're handling ourselves).
You most likely will never outgrow your first box, because you probably won't have m/any customers.
That said, if you want to scale w/o work cloud is really the way to go. Our infrastructure costs are less now with 1bn requests (250TB) over 30 days compared to when we were doing 1k requests/month. That's what can happen when you leverage the cloud. And that's with 2 mostly FTEs. That even includes the massive amount of telemetry we have (which we're handling ourselves).