The easiest way I have found to get gold is to just use an auto-clicker. Just sit your cursor on top of the collect gold button and let the auto clicker collect gold for you while you do something else away from your computer. After that, just sit there going through loot boxes and repeat the process if need be. As far as I am aware, all of the items work like normal loot boxes, so you'll just have to get lucky and get them all normally.

For best results, I turned my auto-clicker to click every 3 and 1/10 seconds as to avoid making the game glitch with having too many clicks in quick succession.

The last thing I can say is if you don't want the potential for any glitches, don't open the loot boxes too fast or carelessly. I haven't run into any game breaking glitches yet, but you can lose gold if you misclick, which will only make the game take longer to complete. Also, do not exit the game without spending all of your gold first because the game does not save your gold amount after closing the game.