From what I have heard, Lady Dawnya is good if you are opening a tea room or shop, especially for the novice.
The World Tea Expo always has good seminars for newbies. But it is a ways off and you could be doing so much now to open in 18 months.
Some of the larger tea vendors should be able to provide some guidance for best selling items and some basic tea knowledge for you. Most employ at least one person with tea expertise and who has helped other start ups get going.
The most successful shop owners do a lot
of research, ask many questions, and visit others shops and cafes.
Do you yet have a business plan? Location?
Now here's my shameless plug: I do work for Adagio and would be happy to help. Feel free to PM me.