Why not just do it on Heroku or a similar system? Then all the difficult stuff is done for you.
If you want to do your own and it is to be a public site then unless you know a lot about the security issues of setting up a server then you should be very concerend. It is not something to be taken lightly.
Further again, if you decide to go ahead, when you say no more than 100 users, it is not the number of users that is significant but how many are expected to be concurrently making requests on the system. If you are expecting less than one request per second then you could likely do it with a Raspberry Pi or similar.
Colin