The kombucha SCOBY is not the same as a vinegar culture, which is only Acetobater bacteria. Kombucha is a mixed culture of yeast (including Brett and Sacch) and bacteria (always w Acetobater, but usually w others, including Lactobacillus).
It's really simple to culture it from commercial bottles of kombucha; Mad Fermentationist has pretty straightforward instructions.
As JonMohno said, stay away from teas w essential oils. From what I've read, you can get away with having a portion (25%) of the tea be herbal, but I've avoided it and stuck with green and black tea.
The strength of the tea and the amount of sugar is pretty variable depending on who you talk to or what recipe you read, so it's more of a to-taste and experimentation kinda thing. I personally have been doing 1 cup of sugar to a gallon and full-strength tea, and have enjoyed the speed of ferment and strength of the final brew.