Cheap is fine, but that pack looks too cheap and flimsy to me.

I did my first Light with this backpack: https://www.amazon.com/dp/B01I6J9ZFC

It was barely big enough for 4 bricks and a 2L hydration bladder, but it held up great. (The only damage was to the zipper pull for a "secret compartment" on the very bottom of the bag -- it got bent by the weight of the bricks sitting on it.) Light events don't put that much stress on packs, to tell the truth. Most PT is done without your pack, for example.

If you're going cheap, a smaller pack is better. A big, unstructured bag that lets your ruckweight shift around a lot will wear you out faster. (I made that mistake on my first training ruck, using a borrowed backpack.)