@educator Hi there. Fellow Indian here. I would recommend DigitalOcean over Vultr due to a number of reasons having used both. However there is a 3rd option which is better imo and that is Linode. 2 main reasons.
Linode offers double RAM at 10$. You get 2gb RAM instead of 1gb for 10$. What I am getting from your post is that you want a 5$ plan. However it will be insufficient for even a small sized forum. Try going for the 2gb RAM option at Linode.
Unless you are a registered business in India you shall have to pay 15% service tax on Digitalocean as of Jan 1 2016. Businesses dont have to pay this tax as long as they dont have a turnover of greater than 10 lacs per annum. This is because DO has officially entered the Indian Market and will need to comply with the Indian Tax authorities. This is not the case of Linode as they dont have an Indian office . This means that the DO plan at 10$ will be more than twice expensive when compared to Linode.
Rest is upto you. Feel free to ask anymore questions
May I suggest that the INVITE function be available to at least admins permanently?
It's an incredibly useful and powerful feature to encourage registrations, case example, if you pick up a few emails while out networking or have a mail database you'd like to use to drive users to your forum.