Predecessor Builds > Iggy & Scorch > Reliable. I don't play ranked

Turret focused build.

Items
Combustion works really well with Iggy's constant turret hits + early 400 mana. Iggy's fire dot will trigger Combustion's aoe. Spirit of Amir pushes lanes quicker (10% monster damage) for river bug and objectives + ability lifesteal when going for fang/orb. Wraith leggings is a good move speed card for Iggy + some magic penn, it also helps Iggy secure molotov kills vs low hp hero's. Oblivion crown is just essential late game damage.
Swap out World breaker and Dreambinder for situational items, otherwise they're fine for sustain and slows. If you don't have spirit of amir by your 3rd card just skip it and get something else that'll have more impact by that point.

General tips: Early game
Try keep you and your turrets separated and away from minions to avoid unnecessary damage. Ward near river on left fog wall to avoid ganks. Wraith and Morigesh can 1 shot turrets using low mana cost abilities from a far, so place turrets further back vs them. Fey can do the same but to a lesser extent. Don't let the other midlaner destroy turrets with their autos. Keep them from pushing turrets by hitting them with spew when they are in range of turrets to keep them alive longer, you want the other midlaner to burn :) mana to destroy your turrets. Push mid before river bug spawns and grab the opposite river bug of your jungler to deny buffs/mana. Avoid getting dove by both the enemy jungler and midlaner when doing this (play safe). Iggy needs either 4 autos or 2 + molotov to kill riverbug early.
Early-Mid game
Callout whenever the enemy midlaner is missing with hp/mana through comms, and if you can see where they went, say what lane they're going to (careful left/right lane). Try counter rotate with the enemy midlaner to cut them off so your teammates don't get ganked. Help your jungler get fangtooth early. You can get mini orb quickly early with help from solo/jungler but if fangtooth is up, it takes priority. Focus on using your ult as cc to push people away from you and towards your turrets. Try not to burn :) your ult too early vs Countess, and (maybe)Argus with their cc. Also definitely don't burn ult early vs Serath's with her I-frame superglue move existing.
Mid-Late game
Oilspill + molotov is our quickest way to clear minions. Save turrets for rotating, we'd want to have 2 going into a fight, try not use too many turrets on minions unless a tower is being attacked. Stay back in team fights, poke with molotov, deny jungle corridors/fog walls with oilspill, try focus the enemy carry/jungle, otherwise fish for kills. Keep placing your wards near the sides of the enemy towers fog walls at mid. Try get your wards to cover as much paths as possible with 1 placement so your team can find out where the enemy jungler is rotating. Ok