I have some Fat Gripz. I think they are pretty cool. Some guys are into thick handled/grip oriented stuff, but most people couldn’t care less. They are pretty versatile, if they seem like fun and you are into grip and forearms, why not? You might use them a lot. At the very least, you give yourself more ways to do curls.
Like dude above, I would say Jumpstretch bands. For a young dude, a Mini Band would be good. Jumpstretch Mini Bands are “Red” bands. Again, this isn’t necessary, but bands are versatile, and cheaper than dumbbells. Pullaparts, Tricep Pushdowns, band GMs, band curls, band leg curls, band upright rows and face pulls. Stuff to do away from the gym. You could use the Fat Gripz as a handle to do stuff with the bands.
To repeat, these things are fun extras, not requirements. But you’d probably be better off with a Mini Band and some Fat Gripz than with an X-Box game or some bigg-ass fancy headphones.
I would urge you not to waste any money on grippers. In my opinion, they are hard to train on effectively and have pretty minimal carry-over to anything else.