There is no answer to your first question... This is very dependent on the flavor you're looking for. I've been kicking around the idea of publishing my thoughts on various flavorings, but it's a huge undertaking, and there are new flavors and companies almost daily.
For example, I was just talking about cheesecake on another thread. I like the LorAnn's cheesecake flavoring. It's about the only LorAnn's flavoring I really, really dig. I use a lot of Perfumer's Apprentice stuff, and I like the way they do business and I really like the quality of their flavorings. However, I personally find their cheesecake flavor to be abominable. It tastes like sweetened cream cheese, but it smells like a fart. I don't mean to be crude, but it just does...
In that same note, Perfumer's Apprentice makes the ONLY chocolate flavorings I've found that don't taste like alcohol. So go figure... There's just a lot of trial and error involved, but if you ask for opinions on any one flavoring, you'll get an earful...
Equipment... You can spend as much or as little as you want.
You'll definitely need bottles, and I find that they vary greatly. Some I like, some I don't, and often for no obvious reason. I'm gonna be a daddy in a few months, so I buy bottles with child-resistant caps whenever possible, but they're more expensive. Good advice earlier, keep an eye out for sales. US Plastics has bottles at wholesale prices, so if you want 100 or so, they're a good source. Otherwise, I typically just keep my eyes open for bottles that meet my specs and buy when they're cheap.
As far as other stuff goes, I use a couple of relatively cheap plastic beakers and cylinders, which you can usually get pretty cheap (couple of dollars each) and that's about it. You'll need rubber gloves, but they're cheap at any pharmacy. Oh, and get some cheap, very small funnels. You'll be surprised how often you'll use these...
Otherwise, you'll need nic, pg, and vg. Look for
reviews. I get mine locally and it's of excellent quality. I buy 100mg/mL nic, which you have to be very careful with, but it's very cheap. You can usually get all of this in the same place at a reasonable price. You can find pg and vg a little cheaper if you're willing to buy it by the gallon, but I just don't see the margin in it...
Hope that's helpful... It's easy to spend lots on flavorings, but it's so worth it... Mixing your own is so much cheaper than buying it premixed that you can afford to experiment a bit. I find that it costs me about a nickel/mL, give or take. And it's fun, until you hit on a fart smelling brew!