All you really "need" is whatever keeps you off of cigarettes. But a you progress, you may find that you'd like more vapor and more flavor. I started on Kanger tanks and when I moved up to an Aspire Nautilus BVC I began tasting my juices much better. The Kanger flavor seemed muted after that. Then I moved up to a Kayfun and I found the Nautilus flavor muted. Then I moved up to RDAs and I found the Kayfun flavor muted.
The more juice in each drag of vapor you inhale, the more flavor in your mouth. Higher wattage gives you a hotter coil that will vaporize more juice, with more flavor and vapor. The wattage that goes to heat your coil is a function of the voltage squared divided by the coil resistance, so you're running 8 watts with your 1.8 ohm coil at 3.8 volts. A lower resistance coil with the same voltage will produce more wattage and vapor. The 1.3 Ohm coil will take you up to 11 watts at 3.8 volts. You can increase your voltage with a variable voltage battery or mod for more wattage and vapor. The Aerotank can probably handle up to 15 watts before giving you dry hits and a burnt taste (where the heat dries out your wick faster than it can saturate and starts burning it.) To handle higher wattage, you need more airflow and more efficient wicking. The newer tank devices like the Atlantis and Subtank can go to 40 watts, RBTA like the Lemo can also go to 40, and RDAs can easily go above 80 watts.
I find 20-30 watts plenty hot enough to give me all the flavor and vapor I want with my Lemo and many RDAs. But six months ago I found 8 watts on my Aerotank satisfactory. I recently bought a 60 watt SX Mini, so perhaps in a few months I may not be able to enjoy anything less than 40-50 watts.
Take your time and enjoy the journey.
Happy 
