Here is what I did.
Research and make some torpedo frigates. Combine them with pulsars and some gunners.
Go out and destroy first gate and hyperspase inhibitors. (I did the most left first).
Create some minelayers and lay lots of mines a bit further in front of mothership (you already know where are they coming from).
Simultaneously take small grp of 2 or so torp frigates, couple of wings of pulsars and order them to go straight across the left edge of map. There is salvageable asteroid field on their territory. If you are careful then you will kill all resource collectors and those where collectors unload. Forgot their names, but they have guns and very good armour, This is the reason not to sent bombers. Why careful, there are some carriers and I think even destroyer nearby.
After you withstand their attack you can build some support and take out second gate with inhibitors. The game after that is a peace of cake <img src="/ubbthreads/images/graemlins/smile.gif" alt="" />
No need to capture all three gates. I captured just one and destroyed the others.
And one thing I just learned is that you can't capture nether carrier nor shipyard. It seems 4 marines is max. They start capture procedure and cancel it near end.
