I like having an assortment of sizes of carboys including a few one gallon jugs like Carlo Rossi wine or apple cider comes in. Well, apple cider used to come in a gallon glass jug. There is another wine, I forget the brand that comes in a jug that's about 3 quarts. I'm talking about jugs that will take a rubber stopper with airlock. I make wine with different kinds of fruit I grow or get from others, so I never know how big a batch I'll get. I have 6.5, 6, 5, and 3 gallon carboys as well as the jugs, so I can split a batch up and then recombine or re-split as the racking goes. Several people are talking about kits. You said you'd start with kits, not a bad idea, but if you move from kits to using fruit or going to a vineyard and picking grapes, then flexibility is helpful. When you get a corker, get a floor corker unless somebody gives you a hand corker for free, which is what they're worth. Oh, I forgot, I have a 14 gallon demijohn I used once and then noticed a hairline crack about 6 inches long along it's equator. They are very thin walled in that area. They're also not recommended for use with a vacuum pump because of that. Speaking of vacuum pumps, if you think you're going to stay with it and do any kind of volume, eventually you'll want one. I use the Allinone and like it.
Regarding tapwater, distilled water, etc. People recommend against chlorinated water from your tap, but you can let it sit out a while and the chlorine will dissipate or heat it on the stove and get rid of the chlorine quickly. I'm not convinced the amount of chlorine in tapwater makes that much difference anyway. When you make bread with yeast, do you use tapwater? Similarly, distilled water not having minerals - your fruit has minerals and you use yeast nutrient, so the minute amount of minerals in spring water or tapwater strike me as being of questionable benefitl.