What are good materials to put around a brick fire pit?

I wouldn't put a fire pit over wood anything.... flammable and will degrade and cause the pit to not maintain level. I would put a pit down over tamped down gravel, decomposed granite and/or sand.

I agree with Sharon and especially like the idea of sand.

Pea gravel or any gravel.

Woodchips = disaster. Here are some handy firepit safety tips.

https://blog.nationwide.com/fire-pit-safety-tips/

https://blog.allstate.com/considering-backyard-fire-pit/

Now you, your family and friends can enjoy a fire! 🔥

Remove the wood chips FIRST!!!!

If you are planning on having much flame, I would dig it down a little, less chance of hot bits and pieces of wood spotting out at you. Build it up a little around the soil level with concrete blocks or something, then enough rocks, sand, gravel or even pavers to cover where sparks can hit without the danger of sparking a fire.