1) fill your own. Your cost will be huge if you just buy prefilled. If hassle free is more important buy prefilled. If you don't want to spend three time more per month fill your own. I have used the cartos smokelesimage sells and I get maybe an hour of fairly consistent vaping out of one before it needs to be topped off. The thing about filler cartos is you will never get all of the juice to the coil. Once the saturation in the filler is down to a certain point it will start to burn. refilling is nearly an absolute must. Just give a prefilled 5 pack a try and get a small bottle of juice from madvapes or some other vendor in the suppliers list here on ecf. Then you can practice refilling and see how you like the overall experience. There are many other cartomizer options available.
2) the feel and operation is a little different. I like both. Auto's give a nice cig like experience and the manuals give more control. Manuals can go off in a pocket and auto's will not. Auto's can be damaged by juice in the switch manuals have a sealed battery. just get one of each and find out what you like better.
3)Volt is a great starter kit. It is a bit pricey when compared to others but not too bad at all. If you want an analog looking form factor get the volt. If you want a battery that will last you all day, look into an ego kit which will cost about the same.
4) Not strictly needed but YES! Nothing worse then being out of the house with dead batteries. Well except running out of juice... or dropping your pv in a toilet... ect...
Bottom line I think the volt would be a great way to start vaping. Give the prefilled cartos a try and see how you like them. Get a small bottle of juice so you can do some refilling. See how it goes for a week, and ask a lot of questions. Good luck