This is for FW
I never change the media unless it is falling apart. All you need to do is to rinse the media out in some tank water, & reuse. <You don't want to sterilize the media .... that kills the biobug.>
For a canister, you can use generic filter floss <polyester batts> or coarse filter foam for your mechanical filtration. <Big Al's sell big sheet of generic filter foam that you cut to fit.>
For your biological filtration, you can skip the expensive ceramic stuff & use (inactivated) carbon. Carbon has a lot of pores & large surface area for the bacteria to grow on. After activated carbon is in your tank for a few weeks, it is essentially inert. As long as you don't have anything nasty in the tank during that time (say meds, chemicals, etc.) that you don't want to risk the carbon leaching back out, you can keep the carbon indefinitely as your bio-media. <You do need to change it whenever you add meds & stuff .... it is NOT as inert as the ceramics.>
You should not need to run chemical filtration unless treating something.
Some people use plastic pot scrubbers as their media. But because those are not compact, it is doable only in large canisters .... it is better used in a wet/dry. <If you want to try this, make sure you find ones without soap, mildewcide or other chemical treatment!!!>