There are some very good advice in here already; I shall attempt to expand this a little further.'

If your budget is $20/month, you can expect pretty good packages with good support. For what you need, though, I don't think VPS or dedicated is necessary at the moment. 15 members isn't much and if your community is small like you say, then it may be a waste to upgrade at this moment.

Have you tried DreamHost? They offer plenty of space and 1TB of traffic for less than $10 per month. Their reliability and support could probably be improved, but since your community is small and it doesn't seem like it's a professional or commercial service, something like DreamHost could fit the bill.