Need help Deploying Sample MERN App to DigitalOcean App Platform.

Hello. I have been following this tutorial on how to build a sample MERN app: https://www.digitalocean.com/community/tutorials/getting-started-with-the-mern-stack#introduction. I think I have already successfully followed the tutorial, and basically what I need help with is deploying this sample MERN App to DigitalOcean's App Platform. You will be responsible not only for deploying the application to the app platform, but since I am using this sample app as a base to continue my code, explaining to me approximately how much this is going to cost me as users/traffic scales up. In addition to this, I would also like to know any other software/problematic libraries/frameworks/etc I may need to install in the future, and if this app platform can support that, so that I can prepare in advance and have that in mind.

Thanks.