Feel free to email me, chris@gorails.com if you have any questions or want to chat and see if it'd be a good solution for you!
Deploybot will allow you to do "git push style" deploys similar to Heroku.
As a "not a devops guru" myself, this combination has served me very well in serving Rails and Sinatra apps.
Edit: If I were based in the the US (I'm in Australia) I would use Heroku. Unfortunately you can't get Heroku in an Australian DC without going on a crazy huge enterprise plan.
this sounds a bit far-fetched to me depending upon the expertise of your friend on both the platforms, he might be more experienced on GCP but not so much on AWS. Anyways my point is devops, in general, is platform agnostic, unless you are going all in on a single provider you can even mix and match few things. As mentioned by many devops gurus, Docker is the absolute must when it comes to things like microservices and devops stuff. I would suggest you compare the two platforms as per your convenience(pricing, brand association etc) then go ahead and deploy your app (monolithic or bundle of microservices) as Docker containers first. Do not worry about scaling at the beginning. Once you get some comfort level on managing your Docker containers you have to move towards automation culture that is the deployments can be done with an automated build pipeline for that naturally as a next step you must use Docker swarm. This process would expose you to the world of devops and microservices/serverless architectures etc. Then you can as a replacement to Docker swarm can try and play with Apache Mesos or kubernetes.
Deployment Tool: Buddy https://buddy.works
Hosting: Amazon EC2, Digital Ocean https://www.digitalocean.com/ , Vultr https://www.vultr.com/ , Azure VM, Google Compute Engine
Go for AWS then. The amount and quality of tutorials, guides and the size of the community is leaps and bounds over Google Cloud. Very useful if you are new to all this.
Btw, for some small/medium scale projects that I have done, I deployed them on DigitalOcean. It's quick and easy compared to everything else. Unless you are running something large scale, you might want to consider DigitalOcean.