I’d honestly go for the $5 basic droplet, and set the different sites up with ghosts; if there is little traffic and they don’t take up that much space, then you should have plenty room for them all, and you can scale up if need be.

Just keep an eye on the usage and see if it’s worth scaling the droplet or moving a site to its own.

Hello, there

Choosing the right Droplet plan depends on your workload. An oversized Droplet would underuse its resources and cost more, but an undersized Droplet running at full CPU or memory would suffer from degraded performance or errors.

In your case, you can start with a smaller droplet and then upgrade in the future if this is needed. I’ll recommend having at least 2GB of RAM.

You can also resize a Droplet to a larger plan after creation, including resizing to a larger Droplet plan of a different kind. For example, you can resize from a Basic Droplet plan to a larger CPU-Optimized Droplet plan. See the Droplet pricing page for a full list of plans and prices.

You can always check our tutorial on Choosing the Right Droplet Plan

https://docs.digitalocean.com/products/droplets/resources/choose-plan/

Hope that this helps!
Regards,
Alex