Hello! Congrats on your new tank!
Is this a typical three tiered media basket?
If so, my suggestion for a good place to start would be with some filter floss in the top tier (where the water first enters). Specifically, I use Poly-Fil, which is exactly the same as aquarium filter floss, but it's much less expensive because it doesn't have a picture of a fish on the bag

You can get Poly-Fil at any craft store or at the craft section of your local Mega-Lo-Mart, it's typically used to stuff pillows and things. Poly-Fil is so cheap it's quite easy and affordable to simply pull it, pitch it and replace it every few days to a week or so:
https://www.michaels.com/product/the-original-polyfil-premium-fiber-fill-bag-20oz-10509852
In the middle I'd try some Granular Activated Carbon.
BRS Rox and ChemiPure are popular choices.
In the bottom I'd add some plastic bio media not so much for "extra" biofiltration, your rocks and sand will take care of that, but to be used if you ever need to quick-cycle a hospital or quarantine tank; plastic specifically because other materials can interact with medications used in QT tanks.
I often use plastic kitchen pot scrubbiest from the dollar store near me, something like these:
https://www.ebay.com/itm/3849703241...K3XlpFMSVZpW2XczGcZytTWTk5W2wGr8aAtiCEALw_wcB
I hope that helps, let us know if you have more questions!
Good luck!