Thanks in advance.
I think for now you can stay where you are. In case the serverspace gets to narrow you can move the installation with everything in it rather easely (see documentation).
At the moment we run more than 20 courses, 10 of them verry active with over 800 students on 400 MB webspace (130 MB used by moodleinstallation). The traffic is rather low (less than 2 GB/month) We have abouth 2000 to 3000 pageviews in Moodle/day.