I'm still a bit of a newbie myself, but one thing to consider is how much tea you want to brew in one go.
If you're drinking high quality, delicious tea, I don't think you'll want to settle for only one cup at a time. But the more you brew, the more leaves you need to use.
It's somewhat counter-intuitive, but let's say you use one teaspoon of leaves for one cup of tea, you can't just steep the same amount of leaves longer to get one liter of tea. But you can brew whatever amount at a time, several times. I think the "10 - 15" times on teapeat.com is exaggerated. It's probably closer to 5, and even then, the taste kind of changes along the way.
I brew something like 7.5 deciliters ( http://theoatmeal.com/pl/senior_year/science ) of tea at a time, and that gives me roughly three nice-sized cups. But I need to use roughly four teaspoons of leaves for that.
If you want to get serious about enjoying high quality tea (and who wouldn't!), you might want to invest in a water-boiler that lets you set the temperature. Almost no quality tea can be brewed at 100C.
For Japanese sencha (my favourite type of tea), it appears that roughly 70C is good, which just so happens to be the temperature I get from my water boiler when I ask for 80C. A lucky coincidence.
Another choice you need to make is the kind of teapot you'll use. A glass pot looks pretty with your lovely green tea in it, but will break into pieces when it slips from your hands when you're washing it. True story. A stainless steel pot won't break, and will keep your tea warm for a long time. Then there are other kinds, like cast-iron pots, ceramic ones, etc. I've got a steel pot now, and I'm quite happy with it.