The key to this build is to take full advantage of the Deth Lazor's long range and aoe to hit as many heroes as often as possible.

For laning I place my turrets 2 as far forward as I safely can then retreat behind minion wave or to a bush and start using the lazor to both harass and clear minions.

For team fights you want to stay back charge to full and hit as many people as possible. Then place a turret down at your feet, and immediately Dismantle and pick up the scrap to reduce the cool down of Deth Lazor from 15 seconds to 6, and the repeat.
In the ideal engagement you place both turrets down near the enemy team, Xplodium Charge, Grav O Bomb 3000, and then charge the Deth Lazor. If timed correctly you can wipe an entire team with this. If people are still alive back up and start alternating scrap and laser.

Once you hit level 16 you can start being much more bold with your engagements as the charging time is cut in half so you don't need to stand in one spot for long at all.

Using this build I regularly top the Hero Damage charts on my team.

The key talents to this build are
Level 1: A few these talents are viable depending on your team comp. I suggest Break It Down! for maximum sustained DPS. Extra TNT is good for more burst with the Grav O Bomb combo. Scrap O Matic Smelter is good if team fights are going to be long. Regen Master is okay on maps like Blackhearts Bay if you don't have a healer and you expect to be roaming Merc camp to Merc camp.

Level 4: Goblin Fusion This is the key to this build. It adds a ton of extra damage.

Level 7: Rock-it Turret XL I take Rocket Turrets hit multiple targets because it maximizes hero damage, helps clear bruisers quickly, and clears minion waves quickly. That said, the other talents are viable in certain situations: Merc Lord if you know you're going to push with mercs, First Aid if you're being focused a lot, MULE on maps like Sky Temple, Black Hearts Bay, or Haunted Mines, and Engine Junk if you are looking to control and gank Sky Temples or Dragon Shrines

Level 10: Grav O Bomb 3000 This is a ranged hero damage team fighting build. Robogoblin doesn't fit.

Level 13: EZ PZ Dimensional Ripper This adds some utility to your Deth Lazor. You will be firing it ofter, and hitting most if not all of the enemy team slowing them all for the rest of your team. It also helps chase and escape. Sprint is okay if you are having a hard time staying alive.

Level 16: Hyper Focus Coils This is the other can't miss talent. It makes you much stronger in team fights and brawls, as you don't have to worry about where to stand to charge as much.

Level 20: Miniature Blackhole This helps you group the enemy team more. You could also grab Fury of the Storm on maps like Spider queen or just if you need to push back lanes.