Tien, I'd refer you for starters to one of the first articles I wrote for TeaRetailer: So you want to sell tea online http://www.tearetailer.com/article_4.html
. My question is, what is your hook? What would make the customer choose you over Adagio, Rishi, and others online. The flip side that you have to consider is what might make someone AVOID you. What would cause them to question your credibility?
As for the number of teas as it relates to your investment, inventory is a pretty small piece of the total investment puzzle. This is not a recommendation, just an example... Let's say, for argument sake, that you're paying $10 to $15 per pound for tea. Buy 10 teas total. Eight single estate teas: 2 white, 2 green, 2 oolong, 2 black. Then buy two tea bases for blending, one black and one green, and a handful of different inclusions for creating blends. For $250 you should be able to come up with a collection of 20 teas without much difficulty. All you need is 3-4 2oz packages of each to get started.
But seriously, if you can't afford more than $250 worth of inventory you should probably not get started yet. A $1,000 budget for inventory would be plenty to offer a collection of 50 teas. Heck, you could just buy 50 existing and proven teas/blends from a wholesaler. All you need is a bag to put them in and some stock labels from an office supply store.
A decent wholesaler can tell you what the best selling teas are. From there, it depends on your niche. There is no right answer to target demographic. If you go after the same exact demographic that works for an existing retailer you'll probably have some trouble gaining traction.