this will largely depends on a couple of things, i.e how many user will be using your VPN server at a time, is it going to be used for big file downloads (traffic), etc.
I’m currently using the 5 usd droplet and its doing fine, but its for personal use only.

Hello, @mbilalshah

As per @hadrianbayanulh reply this will depends on couple of things. To expand on what was already covered. You can choose a droplet in a region that is closest to you and all the other users and keep in mind that you can always upgrade/resize your droplet at any time.

If you want to upgrade in the future you can check:

https://www.digitalocean.com/community/questions/can-i-upgrade-from-a-shared-cpu-to-a-dedicated-cpu

You can also take a look at the VPN solutions in our marketplace:

https://marketplace.digitalocean.com/

and also the existing tools:

https://www.digitalocean.com/community/tools?q=vpn

Hope that this helps!
Regards,
Alex