In the sticky threads at the top of New Members forum are a bunch of useful things, most especially the Newbie videos and the Library thread which will lead you to a multi-part illustrated guide. Check those out - many popular models are mentioned by their real names. And if some interest you, you can find more review and comparison videos for various models on Youtube. Even 2 days of research can help you buy a unit that that performs well and is right for you.
All cigarette-shaped and pen-shaped e-cigarettes are made by a handful of Chinese companies. All of the popular ones can be purchased online under their original model names or numbers for a reasonable price. But other companies like mall shops and fancy-looking websites rebrand them with their own name and jack the prices up. In addition, if you buy a rebranded model and don't know what model it really is, you could be locked into one expensive supplier for all of your replacement parts etc. And even worse, some use modified versions that purposely make it more difficult to refill. It's best to go with a non-rebranded model unless you know what you are buying (what model it really is), whether it's a good model. and whether you are paying too much. As a reference, most average-size ecigarette batteries are $10-15 each, maybe $18 in a fancy color. Most atomizers are $8-10. Cartomizers run about $8 for 5 (less if empty). I saw one rebrander that charged $50 for a battery!