1.8, 2.2 or 2.5 Ohm coils (the standard range of Kanger coils) will work just fine. The lower the Ohm, the warmer the vape.
Personally when I was still using the stock coils I preferred 1.8 as those seem to give the most flavor and vapor. I rebuild all my coils now and prefer 1.5 to 1.7 in my Kanger
tanks.