Predecessor Builds > Iggy & Scorch > Tried and True build.
This is my go to build for iggy. plenty of swaps available for different team comps or different needs.
orb of growth instead of azure core if you want to be more tanky.
megacosm instead of combustion if its a tank heavy team or if you want more objective pressure.
tainted scepter instead of noxia if they have a lot of heals.
lastly spellbreaker instead of caustica if pen isn't needed or you keep getting cc'd early in fights.
With any combination of these you need to know how to position with iggy, he doesn't have mobility and he is pretty squishy, try and stay in the back if possible and if you fight from a fog wall or ledge it's even better. us your ult to crowd control 1v1s to keep them around you turrets and try not to auto cancel you ult for the knock back you lose a ton of damage, your crest with your ult so you have a shield and good life steal when engaging. don't worry about poking too much just keep the waves pushed so you can roam and secure as many obj and river buffs as possible. your turrets are fragile keep them spread apart and have a kill box so no matter which way the fight goes a turret is more likely to be in range. if i can think of any other tips ill edit this