Atomic Green Lantern is a solid pick as a  jungler, and can be devistating in the right hands.

First let's talk about the Mods. You have some choices based on your prefence on how to build. The set-up I have listed is for the best raw stat combos I have found. Running the enhanced Cosmic Belt mod with Empowered Prism is another strong way to build. 

You start of the game buying marauder ring 2. Start with W, not Q. At level 2 you grab Q and start ganking if you think you can get an early pick. With Q's high will cost especially in the higher ranks, it is not worth it because if you miss, you lose a lot of will in one shot, and it is not all too helpful in clearing jungle camps. Your W and passive are what will make those clears super fast. Do not use Q to clear jungle camps!

Now you need to build Ruby of Life. I often go Ruby 1->Dreamstone 1->Ruby 3->Dreamstone 2. As long as I do not blow a lot of will on unsuccessful ventures this gives me all the sustain I will need for the game. As long as you don't kill yourself often, the health bonus and regen of Ruby T3 is all you'll need from the item for a long time so you would not need to cap this yet. If you went with the belt mod, go Belt 1->Dreamstone 1-> Belt 2->Dreamstone 2.

From here I build the reflect piece that counters their main damage sources. I build this up to at least T3 before buying the other one. You often need the armor before capping your first selection. Cap both of these items when you can. Many times I have to build another level into Mar ring during this process to keep up on my clear times and objective control ability.

Staff Route: Now it is time to rush Cosmic Staff. At this point of the game you'll need the damage boost and cooldown reduction. Once you have this cap your skills become extremely deadly especially your ult. Not only will you have a large AoE DoT, but you'll also have the massive AoE healing debuff from wounding. All together you'll have a late game power boost unrivaled by any build that does not use this item. After cosmic staff I will tend to finally cap Ruby and rarely put another level into Dreamstone before I move onto the optional items.

Other Routes: Once you have the reflect done, look at Booster Gold's or Oa Gambit. Oa is stat rich item for enforcers and the aura helps any other PD champ on your team. With Cosmic Belt and Oa at max, you 25 Power Armor penetration. This will eat squishy champions up. 

Booster Gold's is such a great kicker item, you may as well put it as a core item on most tanks The cooldown, health and armor boost are amazing and help you make a lot of amazing plays. The passive at cap is what makes it amazing in the current meta. You can tank a turret or two for your team if and when you wipe the enemy, or if they are very low and guarded. It also makes for great dive plays to pick up kills. 

Now you have a very strong Atomic Green Lantern with the ability to save at least your team before he dies from radiation.

Special Notes:

Q: Start W on Divided, but starting Q is a must on Coast City.

Your Passive and You: Atomic Green Lantern's Passive is what makes his Ult deadly effective, and his jungle clears fast. It scales both with PD and bonus health so you have extra incentive to build him to be the healthy champ he was meant to be.

For Coast City: Atomic Green Lantern can be a top tier jungler in the right hands. When built right he can do a lot damage while having the ability to live through it all. His Ult can send a carry running, or cause an enemy to peel off your carry inorder to chain the pulse to them. This creates a massive disruption your team should always use to their advantage, especially in the mid game where Atomic Green Lantern thrives. Also at the beginning of the match you can pull an enemy into your team making for an easy focus point for the first blood during the jungle invade.