Thanks for playing! I'm glad you're enjoying the game.
As for Leather, even getting 1 Leather per run is usually enough to keep up with boot repairs. One helpful tip is to avoid repairing every time you return to the surface. Since repairs have a minimum cost of 1 Leather, you'll get much better value by waiting until your durability is lower before repairing. Footwear durability lasts quite a while (losing about 1 durability per 10 digs).
If you're still running low on Leather, you can also try spinning the slot machine for a bit. The small wins can occasionally give Leather.
Hope this helps!
