Play 100 (or more) games with Lurker in the kingdom. Try using it in different ways (no Lurker, double/single Lurker opening, odd or even amounts etc.) to see what is best when. Observe how other people use it. I remember it taking me a very long time to work through and develop a better understanding of Scrying Pool and Apothecary(first online expansion).
vsiewnar 3, Seprix 4. Much gratitude to tracer for organising and for keeping on top of things throughout. Your efforts are appreciated! (All I have are upvotes so I gave one to you )