You don't necessarily need ai on 500mg test. It depends on the person. I'm on 1100mg test e atm with zero issues, but I "barely" aromatize.
Wish I could say the same about Nandrolone - I even look at a vial my nips ache.
Its good to run testosterone at a roughly trt dose around 150-250mg at some point to assess whether you need an ai. It's common practice to recommend ai, but each person responds differently to testosterone. Some guys need 1mg of Arimidex a day on 300mg. But you shouldn't just assume you need X amount of ai on X dose of test. Estrogen is anabolic and you will get more growth if you can run test without an ai. Obviously really high test dosages would require some ai, but even on 1750mg of test a week I use like 3 drops of liquid arimidex, which is like .125mg per week - almost nothing.
The best thing is to learn how your body responds to each individual compound, and dosages of that compound. I can't use Nandrolone, even with Cabergoline. A single 50mg shot and my nips HURT the next day. Can't use EQ because it does something to my system that causes disgusting scab formation - like a localize spot at random on the body that has a violent reaction causes wound-like scab buildup which will take multiple weeks to heal from until the EQ has sufficiently cleared my system. My gear was good - I will NEVER touch EQ again.
You can't learn these things without experience and some level of studiousness in how you use gear.
Long story short - I recommend you keep reading the forums and learning.