I highly recommend an ego 510 with the T-cart and T-Atomizers. They allow you to fill up a bit more than a standard cart, don't overflow as much, and if they're clear you'll know exactly how much you have left. They also don't have the material in them that can give you a weird burnt taste. The ego 510 has excellent battery life and a built in USB passthrough which is extremely handy in keeping it fully charged when you're on the go.