How much RAM to choose when hosting Node application on VPS?

I am planning to get either Digitalocean droplet or OVH or Vultr plan for hosting my nodejs application. (P:S - I did digging on heroku, AWS and azure and their growing bills won't be affordable for me).

My application basically keeps track of the student weekly results in test and shows them semester wise to teachers. It has backend where students and teachers can access this data.

What's your opinion on how much RAM is good in such context for real time hosting? Also what's your experience with hosts like - Digital ocean, OVH and Vultr. (or even Linode)