Well, I'd consider that the dark color of the water suggests that the iron is insoluable ferric iron. Ferrous iron, the soluble ion, generally leaves water clear. So you can begin by assuming it's the ferric iron, which is essentially a sediment. So you can start with a sediment filter, which is pretty cheap, the common pleated filter cartridge.
It won't remove dissolved ferrous iron, so if you have that, the water can still stain things, the way it does sinks and toilets. But there may not be much ferrous in your water. If that's the case, you win with a sediment filter. It will also filter for dirt, rust, etc. but will not deal with other dissolved minerals. So heavy dissolved lime might still dry leaving spots. But that's another story, after you see if the cheaper approach works.
Maybe something like this:
https://www.amazon.com/dp/B0016A0JCC/
Cheap enough to try, and you should know pretty quickly if it works. Probably last around 2,000 gallons.
