Is this worth it??

If you really want to get into mtb, you need to do some research on bikes, components, and etiquette. You’ll save yourself so much hassle learning some introductory knowledge.

With that said, youtube is probably your best bet or a local bike shop. As for a bike, stay away from the big box store brands. Look for major staples of the mtb industry, i.e. Trek, Giant, Specialized, Cannondale, etc.

Realistically, $125 is not going to get you anything worthwhile for mtb. You’d either break something or hurt yourself riding trails on a bike like this. I’d say $300 is the minimum you’ll spend on a used entry level mtb. Save your money, do what you can to get bike money but buying decent equipment is a necessity. $500 is the sweet spot for a used mid tier hardtail mtb. Find something like a Cannondale Trail, Trek Roscoe 6, Giant Talon, Specialized Rockhopper.