You don't need to be a cloud expert to start with GCE or EC2 instead of a VPS provider. If you end up just going straight to GCE instead of a droplet that's not a big mental hurdle. Then as the parent said, if you suddenly need to scale up, bolt on other services (like say GCS or Cloud SQL) you're not starting with a migration.
You will spend more than $5/month on either AWS or GCP, but the example here seems focused on a business not a throwaway. So IMO, it is more like premature optimization to have a $5/month droplet instead of a $30/month set of GCE instances.
Disclosure: I work on Google Cloud.