What upgrades should I make for more of an adventure/gravel setup?

I know nothing about bikes but am determined to learn! I got this Rocky Mountain bike secondhand, and I don’t know the model.

I’m wondering if this could work for more gravel/adventure biking, and what type of upgrades one may recommend? Is it worth putting money into upgrading if you don’t know its history or age?

Any suggestions are helpful for this newbie!