Hi Deva,
We're glad to help! We do recommend priming the coil head. Because the coil heads contain a large amount of cotton, priming the coils drastically cuts down the amount of time you have to wait for the cotton to soak up the e-liquid.
For the Eleaf Melo 2, we recommend using coils that list their compatibility with the tank (like the coils on this page).
Best regards,
Brad