Tools for Tea
There are almost an unlimited amount of teapots out there, but here are what I recommend for those serious drinkers out there. Have a few clay teapots, these could be for your roasted oolongs, hei-cha, puer, even black teas. have a nice thin walled porcelain or glass teapot for your lighter oolongs, white teas, and green teas. Have a thicker walled porcelain teapot for black or roasted oolongs if you don't have a designated clay teapot. Get a nice small gaiwan(60-100ml) for when you have only a couple of grams of tea leftover. Something else worth mentioning, is to get a nicer clay teapot, you'll potentially be using it for years, if not decades. 
Note - for the first 10 years of drinking tea I only had one teapot and I enjoyed it all the same. However these recent years I've really put work into my clay teapots and it does really make a difference.
A couple of glass pitchers is all you'll ever need, nothing fancy. The second is in case you'd like to try different teas side by side. 
A strainer isn't necessary, but more of a preferential. It can be used not only to catch the sediments that your tea filter didn't stop, but we use it as a lid on your pitcher to keep your tea hotter.
You never know who will be there or trying different teas side by side so four cups is a good number to have. Thick walled to keep heat in, yet smaller to stay in accordance with a smaller teapot. 
Coasters
These aren't so much of a must, but if you have wooden furniture, the near boiling hot water in a teapot, cup or pitcher could leave permanent marks. 
Scales are a great addition to help you figure out the specific way you like to brew your tea.
Vessel(Cha He)
A vessel would be something to transfer the tea from the scale to the teapot, this could be anything with an open mouth to pour out of.
There are a couple of ways to go here, the standard water kettle, and a water boiler. Our recommended water boiler is the Zojirushi. It keeps your water at a stable temperature of your choosing so you don't have to reboil every time you want tea.
This could possibly be the most overlooked aspect of a good cup of tea. This could be anything from a portable water filter like Brita to our recommended reverse osmosis system that hooks directly into a water line.
Tea Board
Tea boards aren't necessary, but another great addition in your tea collection. These again, can be anything from a small board just big enough for a teapot to more than a couple feet long. They also can have drains at the bottom or a small reservoir. They can be made out of wood, stone, or even plastic or metal. 
This is obviously the the most important part. Explore and taste as many teas as possible. Find sample sets and see which types of tea you like. Even so much as the year it was produced can make a tea completely different. 
This is a nice something to have for those out of town trips, hikes, or picnics.
At the end of the day, any type of tea, in any type of teapot, with filtered or unfiltered water beats not having any tea at all. These are all great ideas to buy gradually and to gift or be gifted.