Should I buy what kind of droplet of Digital Ocean?
From the official install guide – Discourse requires a minimum of 1 GB RAM for small communities; we recommend 2 GB RAM for medium communities.
1 GB RAM = $10/Month
2 GB RAM = $20/Month
To give you an idea, my forum has about 150-200 posts per day and is running on a 2GB Digital Ocean instance. It is at about 70% memory usage.
Which cloud hosting is reliable