For $50, I'd be looking at how I could accessorize, maintain, or make what I've got better.
Stuff like:
Hydration bladder and ITW strap Dominators for a pack.
Better stuff sack/s, or accessory pouches for specific gear.
New stove, or water filter.
Supportive insoles, and good socks.
Nice baselayer, or headgear.
Sleeping bag liner.
Strops/paste, maybe a diamond stone.
Spare battery, or super-duper memory card for a camera.
Custom kydex for a favorite knife or two, or custom scales.
Battery charger, Pelican case, extra rope, cord, or webbing, performance wash for wool, softshells, baselayers, jackets or sleeping bags, DWR spray for shells, gaiters, new sleeping pad, better compass, trail maps...