Moving from free discourse to self hosted discourse

How would I go about moving my Discourse site and all it’s data hosted by https://free.discourse.group to a hosted discourse on digital ocean.

Do I have to get a backup?

Also how much GB is recommended to buy for a 80-100 member site and raising.

do you have a backup section in your admin panel ?

site.com/admin/backups

if so, just make a backup and restore it on the self hosted site

1GB to start off should be enough

Alrighty, when would I need to up the storage amount? At about what amount of active users.

it would depend on how many images people upload and so on.

Your SysAdmin would be able to keep track of the space usage and should advise accordingly