For me, personally, without relying on the Algol glitch, the fastest way I could get gold (as well as working towards the all equipment achievement) was Tower of Lost Souls 11th floor, where all four enemies set themselves up for easy grabbing. Using Cervantes, the basic A+G grab can ring them out as soon as I push them towards the edge, which is not hard. Finish the floor in just a few minutes (or less if they're dumb) and it's 4500 gold. You can also complete the critical finish achievement on this floor by using Yun-Seong's forward Y, Y move incredibly quickly. Keep running to push them towards the edge and you also work towards the 10k m achievement. A lot of things can be done at once here.