How to understand what resource is needed for hosting?

Question

Network administration

Help me to understand. I have several dozen sites, mostly developed on the basis of WP or OpenCart.
I need to understand which hosting to choose. Intermediaries are not suitable, I want to save money (I understand that it will be necessary to deal with a lot). I was advised to use digitalocean.
1. On average, about 1000-2000 visits to each site.
2. The site can have 100 visitors at the same time, there were more.
3. There are sites that have up to 100 visitors per day and up to 10 visitors at the same time.
What resource do I need for 100 concurrent visitors?
PS Perhaps I wrote stupidity, I wrote it as I understand it. I ask for a human explanation.

Answer 1

1. We take a server so that there is guaranteed enough space, memory and processor for a dozen sites
   Such things are not done in 2 clicks.
   Hardly save. The administration of this economy also costs money.

Answer 2

Choose the minimum and then raise if necessary
. It seems to me that it is extremely difficult to save on digital ocean

Answer 3

Take it to ru.hetzner.com Perhaps not the cheapest, but at least stable.
In general, it would be better to use the services of resellers. They will cost a little more, but administration can sometimes play a key role. Here I would advise unihost.com