Hint: This Hint thing is stupid. Can we stop this?
Secondary Hint: How are you generating your essence loop anyway? This looks cool and fun but you've provided very little info on how this actually works. It's one thing to see blocks, it's another to know what you have in them.(plus I can see Thermal Expansion blocks, and that's a very fuzzy zone for me since they aren't very visually distinctive to me)
Oh fine.
There are lots of ways. Ars values items based on their rarity in vanilla. Mods let you create a lot of vanilla-rare items in easy ways. The pulverizer, for example, turns stone bricks into cracked stone bricks. It costs 300 essence to fabricate a stone brick and is worth 4500 essence as a cracked stone brick.
Used to be that simply making cobblestone slabs would triple their value, but the vanilla only changes, with a crafting table, have all been removed. So it's really only in a mixed mod environment that this even comes up. Look for some way to generate vanilla items (because that's all Ars will give value too, unless you configure it) that can easily be generated. Don't just throw that cobblestone in, or pulverize that cobblestone to sand (which actually lowers its value), use a factorization grinder to turn it into gravel, and pulverize
that to make flint, valued at 7 times the cobblestones value. Because flint is a paint to get in vanilla.
If you start looking at just general farms...well, leaves are worth 70 essence each. MFR farms will give you leaves as easily as pressing a button. There are a lot of leaves in a tree.
Very little will beat that 4200 essence profit in just a few seconds though.
The default install of Ars I initially used recognized copper and tin and would fabricate it as well, but KirinDave is a big meanie.