If efficiency is your thing, it's perfectly possible to ignore factories altogether...if you build up all your planets with nothing but research facilities, you can get enough production from the focus buttons to maintain a military. Not as absurd as it sounds....whilst you will only produce ships very slowly, it won't take you long to have such a strong tech lead they'll be almost invincible.
A strong economy is vital. Not only are you GENUINELY spending at very nearly 100% of capacity, but also if you plan on building up the planets you conquer, you will probably have to buy the first few research facilities in order to get the rest built at a reasonable rate. (Personally I don't bother with that...I just use the extra income to finance extra production around my core planets via economy starbases. This is also more cost effective since you get half the bonus for free.)
You could also take the mirror image approach. IE build nothing but factories and focus on research. This approach is even more viable because:
a) There's no need to carefully balance exactly when to make the shift from military/social spending to research spending.

You don't have the problem of it being very slow and/or expensive to build up your conquered planets.
c) Can't fund full production yet? No problem. Just don't build ships or social projects on a few planets. With the research based strategy, if you want useful production levels you HAVE to pay for the research. The other way round you can get the research without having to build anything at the time.
Also, nobody is going to be able to beat you to construction of the wonders. Even suicidal is not too bad with this strategy, at least WITH tech trading. Without tech trading...I suspect it MIGHT still be possible, but you need a little bit of luck with starting positions. An early war will cripple you since your ships will be well behind techwise.