As little as possible, preferably 0mg. The first cycle sticky here recommends 1/4mg EOD, this is good for a first cycle. As you get more experience under your belt, the goal should be to move away from AI and run just the minimum you need to avoid negative estrogenic sides.
In time, I think you will find other compounds (like the DHT derivatives) that you can run instead of a dedicated AI. They bring the dual benefit of controlling estrogen and having at least mild anabolic effects.