Sorry to hear youre having problems.
Just to clarify, I have gyno. I haven't taken any form of AAS in my life, be it traditional AAS used by bodybuilders or prohormone/designer steroids available OTC. I have considered it in the past though, and have read up extensively. I can't offer any real life experience, just the advice of someone who's taken a large ammount of time educating himself on AAS use, and deciding it wasn't for him.
For anyone susceptable to gyno, the most commonly used mass building AAS can be your own worst enemy.
Take a typical cycle of say 500mg test weeks 1-12, DBol 30mg weeks 1-4, Decca Durabolin 300-600mg weeks 1-12:
Youre kick starting the cycle with dianabol, which can readily aromatise. As it's a methylated hormone, it'll aromatise to a Methyl-Oestradiol, bad news for gyno, very bad news...
Test obviously will aromatise to all the forms of Oestrogen that natural test does in the body. It's the Decca that can REALLY cause problems tho. Nandralone is a progestin, capable of stimulating progesterone receptors 20% as eficiently as progesterone. This is the main reason for it's ability to shut you down hard and fast. It can also combined with an elevated oestrogen level , cause progesterone related gyno.
If you're experiencing gyno due to progestenic activity, all the Nolvadex and Letro in the world will not stop its progression. There are a few anti-progestenic's available such as Bromocriptine, which could help during a cycle including Decca, however I'm not sure about its effectiveness to treat gyno after it's occured.
Are you still on cycle at the moment? If you are I'd strongly suggest you at least stop the Decca mate!! I know it's an extremely long lasting ester, but still a wise decision. Sounds like you have no way to combat progestenic sides. Don't run Decca without Bromo, it's asking for trouble when combined with test.
When you come into PCT (21-28 days after last injection) continue to use letro, and tasper off it slowly.. very slowly. You could otherwise experience some wicked oestrogen rebound, causing your gyno to flare up again.
AS for eliminating side effects.. you can't really, just minimise them. Use steroids that don't aromatise, such as EQ, Tren, Winstrol etc. A small dose of testosterone with NON progestenic steroids should do no harm ie 200mg of testosterone per week. If you do experience chest symptoms from the test, don't taper up an AI, start it at a high dose, then taper DOWN when the side effect stops.
AI/SERM usage as soon as glandular tissue starts to develop can be effective from the many many testemonials I've read. The older the tissue however, the less of an effect Nolvadex will have.