Hi there @josephClam,
Choosing the size of your Droplet would really be based on a lot of factors. If you are already hosting your websites somewhere else, I would recommend checking your average resources’ utilization like RAM & CPU, and base on that, you can then make the decision.
Another thing that I would suggest is also checking the size of your websites and choosing a Droplet with enough Disk space for your sites, or based on that information you could decide to add block storage to store some of your static files for example.
Another thing that I usually do is to run some stress tests before releasing a new site:
That way you would know how your sites and server behave based on the different amounts of traffic.
Of course, the best part is that if you ever need to, you could always upgrade your Droplet, or move some of your sites on a separate Droplet if they need extra resources.
Hope that this helps!
In this article, we'll talk about the server side of web performance optimization: how fast can your server respond to your user's requests? We'll review the general landscape of load testing, step through a plan to find your server's maximum practical response rate, and discuss some options for open source load testing software.