Different steroids cause different types of gyno for example while running testosterone you may face estrogen related gyno which could be treated with several drugs....(this isnt all of them)
1)Nolva (SERM)
2)A-dex (AI)
3)Aromasin (AI)
4)Letro (AI) *Letro is the strongest of all and should only be used when truely necessary more for treatment than to prevent gyno.

There is also prolactin gyno which usually is caused by 19-nor steroids such as Deca and Tren. This can result in Lactating from the nipples. This gyno can be prevented or treated with the use of these 2 drugs:

1)Caber
2)Bromo

This is just basics but in my opinion you should do more research before jumping into this.