To brew 1 gallon: Using a large glass jar & Mother scoby (the yeast film layers on top of the tea), carefully pour out all of the kombucha into a mason jar(s) accept leave approx. 2 cups in the jar of kombucha, this is called starter tea.
Feel free to filter the kombucha that you poured out. Put the mason jar(s) in the fridge to prevent continued fermentation. Of course you can flavor it with fruit juices, almond or other flavorings if you wish.
Brew 1 gallon of black, white or green tea (not herbal tea). While still hot add 1 1/3 C sugar or honey or brown sugar. Stir until dissolved completely. Allow to sit until it's at room temperature. If it's too hot, it could kill the yeast/scoby.
Now in the jar with the mother scoby, add the sweetened tea slowly. Allow to sit undisturbed for 7-21 days, tasting with a straw each day after 7 days until it's to your "brewed" taste.
And then start the process over again. With every batch of kombucha tea you brew a new scoby will form. you can just leave the scobys together or separate them and give one to friend. The older your scoby gets, the darker and thicker it will become. Your scoby will last for years if properly taken care of. You can also carefully peel the mother scoby in half or in thirds, place carefully flat in a gallon Ziploc bag with 1 C room temp kombucha to share with a friend. The scoby and kombucha because of the yeast need to breathe so your friend(s) will need to carefully use their own jar to start brewing with their new mother scoby within 12 hours of the scoby being sealed in the Ziploc.
Your scoby may get air bubbles or "strings" or brown things, that's all ok. If it ever forms mold, throw it out!
If your original scoby was small like from a wide mouth mason jar, it may float sideways or others. That's ok too!