You can start RRL tea anytime, although if you have a history of miscarriages, you'll often be told to wait past the first trimester, especially if it causes you to contract any.
I have been meaning to drink mine from the start, but never got around to making it.
I got the loose leaf herbs from Mountain Rose Herbs, and I think I did vanilla flavored red rooibus as a base, then added RRL, nettles, rose hips, alfalfa, and maybe something else... it's been a while. Toss lots of honey in there and drink it hot. YUM.
My problem is that I'm lazy and don't end up making it everyday, and I can't just do a big batch that lasts a few days because I don't like to drink it cold. Oh well. One of these days, I'll start making it again. It is really good for you! I was drinking it some while TTC, and when I drank it a whole cycle, it really did help my cycle some.