INFINITE GEMS:
After getting 100+ gems, save the game, open multiple tabs of Idle Mine, and craft using multiple gems ONLY on the duplicated tabs. If you don't get a pickaxe that you like, then close the duplicated tabs, and save the original one so nothing happened. Then repeat. If you DID get one you liked, save that one and close all the others.
With the birds, the mass spike spam, and ridiculously hard levels, forget the tower. I'd keep the money i already have, this job didn't even have a health plan.