If I had to give advice to a random person with non-specific needs, it would be to pick a full-suspension rig in the 115-130mm travel range, with as good of components as you can afford, fit it properly to your body, and install the right tires for your local terrain. Then go ride it until your legs fall off and your lungs catch fire, and repeat as necessary. If you're lucky enough to live in an area with terrain that requires more travel, awesome; buy a 150-160mm enduro bike, and please invite me on a ride someday. If you live in the upper Midwest and ride in two seasons ("snow" and "sand"), maybe buy a fat bike instead. If you want to do something like 60% gravel, 20% road, and 20% trail, go buy one of the latest gravel bikes with a suspension fork and flared bars; it's basically like riding a 20-year-old hardtail MTB in a slightly more aero position.