I got a kit through OpenSky from Kombucha Brooklyn for under $40. (I had a $10 credit and a free shipping code - score!)
https://opensky.com/brendanbrazier/product/kombucha-home-brewing-starter-set-by-kombucha-brooklyn It includes everything you need to make your first batch; you reuse the culture for subsequent batches, so it's pretty much a one time purchase. (to put it in perspective, that $40 is about a week's worth of bottles, and it makes a gallon. yeah, easy math, even for me.)
First, you boil the water. (yes, I took a picture of water coming to a boil... didn't want to skip a step). Then steep the tea bag(s) for 20 minutes. Add the pure cane sugar and stir to dissolve. Pour in cold water, then add it all to the fermentation jar. Check the temperature (they even include a stick on thermometer so you don't kill your SCOBY - more on that later.), then add the culture, known as SCOBY or mother. Cover with a breathable material, secure it with a rubber band, and let it ferment in a darkish corner for a couple of weeks.
Now, info about the culture - SCOBY = Symbiotic Colony of Bacteria and Yeast. AKA Mother. She is a gelatinous disk of live bacteria that eat the sugar and produce the fermentation that turns sweet tea into a jar of bubbly love. It is also the same culture that turns wine into vinegar, hence the vinegary taste and aroma of the 'buch. I could get in to the biology and etymology, but I'll leave it up to you to hit Wikipedia up for that info. As long as you treat her well - keep her fed and resting comfortably in the low 80's unless you're storing her in the 'fridge between batches, no direct sunlight, nothing too rough, etc. - she can reproduce pretty much indefinitely. She will create children with every batch, which can be used to make more immediately, stored in the 'fridge with some of the fermented 'buch to nap until it's time to brew again, or shared with those you love so they can make their own. I know people that have used the same mother and children for years, and have supplied lots of friends with their own. Once I have a few children, I'll start sharing, so be nice to me ;-)
I'll post follow ups as this process continues.
love and peace.