I want a camera for my hobbie. Which camera should I start with?

I'm not rich. I want a camera for making videos, taking pictures at conventions, interviewing some people, blogging, etc.
It's a hobby I'm starting. I have an Iphone 4. I've been using it alot. I fill up my 16gb memory in less then a week. Should I just continue using it or should I invest in a real camera?

I have, at most, a hundred I can spare right now. I can save up more.

What camera would you suggest, if at all?

Strange request.
I use craigslist all the time. If you could search through it to find a great camera for me, that would be great.
http://sandiego.craigslist.org/
or amazon! Whichever.

Many still cameras have video functions, and especially the DSLRs with video produce decent enough results. If you only want to record an occasional video clip, then sure… No problem.
However, if video is important to you, you are MUCH better off with a camcorder.

At this point in time, they still do a much better job (and are much more user-friendly) at video and audio recording than still cameras can.
Try your question in the camcorder section - perhaps someone has an idea that stays within your VERY limited budget.

For a hundred bucks your not buying anything. Any good that is. If you wanted a good started DSLR then I'd go with the Nikon D3100 D3200 or Canon T3i. All of which are out of your price range but will do what you ask of them.

Basically save your money for a while longer. A hundred dollars will buy a camera that has the same video and image quality as your i phone, maybe even worse.