The same options every business that needed them has done for decades? Renting dedicated servers én masse, colocating, or running own datacenters? And doing this in multiple countries?
What I'd suggest for a start is renting dedicated servers or colocating in a few places (EU-Central, US east, US west), and running on that.
Dedicated servers, even with having to maintain them, are always cheaper than GCP. Even more so is the network traffic.
I've started with dedicated servers with a few European hosters myself where I'd be able to get servers and traffic for 40€ a month that would have cost me upwards of 14'000€ a month with GCP, AWS or Azure (180TB+ traffic per month, I don't have the exact numbers again, but I used each service's cost calculator for this). Sure, if I want high quality networking, I'd have to pay another 360€ per month extra with these hosters, but that's still cheap enough that it means I can basically run a 180TB/month serving service on a hobbyists budget.