So does that mean that I can't just buy a fancy looking (mechanical mod) E cig that has all the battery, electrical parts etc included?
Yes you can (sort of) however it won't do much for you unless you know how to get the best out of it. If you're a new vaper you're probably not there yet.
It's a bit like buying the most expensive camera in the shop to take good holiday pics, if you don't have the know how to use it well then a much cheaper point and shoot camera will suit you much better for a little while.
Vaping is a balancing act between 3 things the airflow, the power level, and the wicking. All ecigs are basically a heating coil wrapped around a wick. A battery powers the coil and heats it up, you draw through the mouthpiece and inhale the vapour.
the most basic starter kits are a fixed voltage eGo style battery (an evod battery is an eGo style) with a clearomiser like an evod on it that you fill with your chosen e-liquid. Using one of those you'll get an OK vape but you have little control over the quality of the vape. A bit like using the camera on your mobile to take pics.
the next steup up from that add variable voltage which lets you turn up or down the power sent to the coil. More power makes the coil hotter and hotter = more vapour and more flavour.
Next step up from that is a VV/VW mid range mod. An SVD an MVP an itaste VV or a Vamo are all good examples. they do more or less the same thing. The MVP and VV have built in batteries. The SVD and Vamo take rechargeable batteries and you need to also buy a charger and batteries to go with them.
All of them provide more 'ooomph' and give you more control over your vape. they also let you set it in watts or power mode. this is like "automatic volt control" though if you prefer you can change the settings in manual voltage control. This is a bit like your point and shoot average camera. (If you want to you can use manual mode, but you'll get good results if you set everything to auto, and it'll take better photos than your phone will)
Then you get to mechanical mods (the shiny ones that have the sexy engravings) these are completely manual. they provide the coil with the power that comes direct from the battery, no more, no less. When the battery is charged fully they are more powerful than when the battery is half charged, and will vape differently. You need to know what resistance the coil you're using is, what power level you prefer to vape at and how to tailor the coil you use to get the vape you want from the provided voltage. (which might all sound right now like gobbledegook but it's easier to pickup than it sounds) You can get a really high quality vape from a mech, once you know what you're after and how to get there. A bit like a full on everything manual camera with no automatic mode.
A mid range mod like an MVP or SVD and the batteries and bits you'll need in a full kit will set you back about £50-70 including a tank/clearomiser and some liquid, depending on exactly what you get and where from.
Once you have a mod the running costs are just replacement coils (or supplies to build your own, which is easier than it sounds) and e-liquid. Both of which are pretty cheap.
You will need a backup device of some description so even if after a couple of months you have picked up what you need to know and go for a flashy shiny mech you'll still have a use for your old device. If you go for something that takes batteries then you'll already have the batteries and charger you need for that. Any of the mid range mods will double as a useful coil resistance checker as well later down the road if you want to end up with a mech where checking the resistance of the coil before you use it is essential. (shorts are really bad)
Don't go too fast though. Pickup a midpriced mod that you like the look/features of for now and learn which liquids you prefer and which power settings you like and learn how to get the best out of that and then go for the super, shiny upgrade a little later on.
