You are not getting a 100% chance to target a boss or additional boss every time. That's the RNG aspect of this game. So you can not catch each chance of abundant currency dropping. But if you want to farm over 3000 Flame Elementium in Torchlight Infinite, this article that references Squejeee's video will give you some tips and tricks.
Dark Surge Is Really Good for Embers
It would help if you ran maps as fast as you could because the monsters that you spawn in at the end of the day are magic monsters, and they will draw members. So you can beat the boss at the beginning, save those embers dropped by monsters, and sell them for good money.
Dark Surge Cards Are Good for Rewarding Memory Fragments
Besides, you can get a lot of good currency from Dark Surge ember farming. You occasionally can get the two boss cards. If you see what cards you have stacked up and make the right decisions based on those cards, a lot of the Dark Surge cards drop memory fragments. If you know how these cards are running and what they can do, you can get more memory framings. For example, when you get two good Dark Surge cards for memory-fragmented rewards, you can use compasses to duplicate those memory fragments.
Getting More Cards Is Good for Rewarding Gear and Commodities
Besides Dark Surge Cards, there are a lot of other cards in Torchlight Infinite. You can use those to get a little bit more juice out of your cards, such as Honest cards. When things aren't going your way for getting Dark Surge Cards, this is a good way to help you to get Gear and commodities when you run these cards.
You Can Sell Gear That You Are not Needing
You can sell everything you don't need when your character is fully kitted and you have crafted all high-level Gear.
For example, you are not going for Timemark 1, so you don't need Divine Arbiter's Feet right now. Your character does Timemark 7 and Timemark 8 maps, and he does League mechanic difficulty and things of that nature, so you don't need to be perfect on all your Gear to work. Then you can sell these Gear, including Divine Arbiter's Feet, Embers, Flame Sand, etc.
You Can Put Some Compasses on Your Maps
You can throw compasses on maps to roll a good quantity of items.
You Can Run More Maps to Farm
When you run maps as fast as you can, you can easily get more additional currency and meet more chances of dropping memory fragments.
With the above, you can get a lot of resources that can change to Flame Elementium.