Hermit Crab Advice Needed

Hi everyone! I'm brand new to keeping hermit crabs and would love some advice on my setup so far. My daughter was gifted a hermit crab for her birthday, and I'm trying to give him the best life possible.

Right now he's in a 10-gallon tank with coconut fiber substrate that's deep enough for him to bury. I added some aquarium plants for cover, a food dish, fresh water, and a lid to help retain humidity. The room stays around 72°F, so I know I need to get both the temperature and humidity up to the proper levels.

Here are the upgrades I'm already planning:

Mix play sand into the substrate.

Add more climbing opportunities (cholla wood, branches, etc.).

Provide a variety of natural shells in his size.

Offer a more balanced diet instead of just fruit.

Install a proper heat mat.

He buried himself shortly after I brought him home, stayed underground for a couple of days, and has now come back up and started exploring. Is that normal for a newly rescued hermit crab?

I'm completely new to this, but I'm genuinely willing to learn and do whatever I need to in order to give him a happy, healthy life. I've also read that hermit crabs are social animals, so once I have the habitat set up correctly and can properly care for them, I plan on getting him a friend.

I'd really appreciate any constructive feedback. If you notice anything that should be changed sooner rather than later, please let me know. I'm here to learn, and I truly want to give these little guys the best home possible. Thank you so much!