The Darkness II

You learn about Jackie's Talents near the very beginning of the campaign when you unlock the Jackie's Got Talent achievement. Throughout the game you will earn Essence by killing enemies, breaking lights, beating bosses, etc. It will probably take you around 2 playthroughs of this game to earn enough Essence to purchase all of Jackie's Talents, but luckily you need to do 2 playthroughs anyway in order to get the At Home in the Dark achievement for finishing all chapters in New Game+ on any difficulty.

I suggest looking over all of Jackie's Talents and choosing which ones you want the most and working towards those first. You'll get the rest over time.

The key is to make interesting kills, not just execution or gun kills.
At the beginning, your enemies are mainly mobsters. Execution yield 30 dark essence, while headshot is only 20, sure you get to eat the heart but it only offers 5. So execution is the best way to go until you have meet up with your Darkling.

Now that you have your Darkling, allow him to attack the enemies and assist the kill with objects, make sure it is sharp as not all objects can kill in one shot. With this type of kill you get throw bonus 20, and Darkling assist bonus 10, now with heart eating 5, you get 35, better than execution, in fact from now on, execution is pretty much useless if you want to maximize your essence count.

Once you have enough essence (1000), purchase the "Fly Darkling" ability, so you are able to throw your Darkling towards your target, purchase this skill as quickly as possible, since it is the most useful skill to learn for essence collection, reason is Darkling does not always attack enemies in an area automatically, and will not attack stronger enemies at all. So with the new power, you can use your left demon Arm and throw him at the enemies, and once he latches on, use the right demon arm to kill it. But do so quickly because you only get a small window of opportunity before the Darkling kills the target. Darkling kill only gives 20, while demon arm kill gives 20, plus Darkling assists offers 10, plus heart eating, you are looking at 35+. I used this method all the way from Chapter 2 to the end. In the end, one Brotherhood enemy can give as much as 55 dark essences.

Now some time during the game you may lose your Darkling or Darkness power. during such time plan ahead, mobsters yield maximum of 30 essence, so execute them is the best way. When you only have you weapons, then headshot is the best which gives you 20. Controlling Darkling can yield maximum 30, so let Darkling execute target if you are in such situation. Finally when you only have darkness power, and facing the Brotherhood, always kill them with right demon arm, and then eat their heart, as Brotherhood soldier always yield more dark essence than boring execution.

Finally, shoot the lights, collect Artifacts, and if you have the Limited Edition bonuses, purchase the exclusive "Gourmet Heart" ability as it give 20% bonus essence for each heart eaten.

EDIT:
Now that I have finished the first playthrough, I was 5000 dark essences short of getting this achievement. I didn't have the Limited Edition bonus, so I guess it is impossible to get this achievement in just one playthrough, unless you have the exclusive "Gourmet Heart" ability.

I achieved this during my New Game+. I dont believe you can get it in only one playthrough.

Basically there are 4 talent trees to fill out, you need essence to fill them out. The ways to get essence from least amount to most amount are...

Destroying lights
Devouring Hearts
Killing enemies with a gun
Killing enemies with misc weapons (impale, sliced, swarmed, darkling)
Blackhole
Executions
Beating Bosses
Collecting Artifacts

During your playthroughs, to max out your essence gathering the fastest its recommended you perform any of the 4 executions on as many enemies as you can, those give 30 points of essence each. By collecting artifacts you gain 300 points.