I believe the resistance range is 0.1Ω to 3.0Ω, so anything in that range will work. You'll want to start at a lower wattage to avoid burning, then increase the power incrementally until it's performing the way you like. Generally, higher resistance coils will be made with thinner wire and will need much lower wattage than low-resistance coils. You'll also get better battery life with higher resistance and/or lower wattage.