you can find a lot of used aquarium and equipment in your local adverts. I still have a lot of aquarium stuff I need to get rid of since I stopped running my tanks. Learn the nitrogen cycle, and keep things simple. Aquarium shops will try to sell you a bunch of expensive stuff that you don't need. Get good filter media (porous rocks with a lot of surface area to allow beneficial bacterial to grow for the nitrogen cycle), you never need to replace filter media. If the flow of your filter slows down, just rinse the media with tank water.