Ariel, why don't you look around on your local craigslist? I see people selling lots of fish supplies for very cheap, and people even regularly give things away for free. You can get away with not using a filter if you commit to doing water changes every single day, but in the long run it's much easier to use a filter.
It's very wise of you to decide to wait. There's no point in putting another fish in that tank until you're sure you have the perfect environment for them, otherwise they'll probably just die again.
Why don't you look through this link?
It details all the requirements for taking care of a betta. That way you have all the information you need in one spot, you can even print it out and check it off until everything is taken care of.