I would recommend Raloxifene. 120mgs/day week1, 60mgs/day every week thereafter. If you have nolvadex you can use it as well. It is almost as effective as Raloxifene. Take the Nolva 40mg/day week 1, 20mg/day every week thereafter.
Expect to take for months. This takes time. Most gyno studies run 6 months. It will take 2 months to start to see significant changes. Thats just the way it is if you want to treat gyno properly.
Do NOT use an AI like letrozole to try to treat your gyno. It is unhealthy, uncomfortable, and not as effective as raloxifene or tamoxifen. Letrozole will totally crush your e2 levels sytemically. This is very unhealthy and very unpleasant. You feeel like shit, you have no energy, no sex drive, you will have ED, its a nightmare.
On the other hand the serms will simply block the e2 from acting on the estrogen receptor in breast tissue- right where you want too. It literally starves the cells of estrogen and they die.
If you are lucky you will successfully reverse your gyno. If you do not using raloxifene following the above protocol sadly your only option is surgery. If ralox wont kill it it will have to be cut out.