If you knew my character Yucie on Elsword, then you'd know that I've been a market hound since I joined and I had quit before the henir revamp arrived.
I've been able to amass over 7b ED without spending real money on the game, and just using basic marketing tactics.
From what I've understood about the current economic state, it shouldn't be all that difficult to amass enough for any burner set at all, my friends have also been taking to the market for a while and making more than their fair share of ED for all they need as well.
If being a merchant and babysitting the board for resale isn't your cup of tea, then I hear that Henir cubes are worth a fair bit as well as secret dungeon tickets and crafting pieces if you're more of the farming type.
Also helps to focus on a single main character instead of several all at once.