If what you have is a 510 threaded (of Ego then it is) - I think Joyetech Smart Carts were a brief failed attempt which quickly were replaced by the
tank atomizers and
tanks (rather than smart carts trying to use a normal atomizer).
Most people use cartomizers. If your model is slim 510 try 3 ohm Boge cartomizers. If you model is fat like Ego with 450mah or longer charge, you can use the hotter 2 ohm Boges though the 3 ohm may be easier to learn on (more forgiving, a bit harder to singe)
Note - if your atomizer is a tank atomizer with a spike in it then they are
tanks, not what Joye called Smart Carts which were used on normal atomizers. If you do have a tank atomizer, the wick may need to be adjusted somewhere between burning and leaking.