Idle Skilling

Idle Skilling

Construction : Craft tips?
I am willing to craft Mach Speed, a craft from the 2nd tree, but it requires 4.4T things from the forge... (for lvl12)
Where on earth can I get that much ... things from the forge?

And I am also willing to craft Big Boy Bags (3rd tree), but it requires an insane amount of gold coins (45QQ). Is the only way to get those is to farm like hell for Sigils to exchange them for gold coins?