Going from the start without the initial building from the new patch, you should start in this order
Power Generator = PGen
Mass Extractor = ME
So place these in a row like this :
(1.) ME....|
Space for a mass storage but don't build it now
(2.) PGen.|- (4.) Factory (placing the factory so it is adjacent to the ME and PG's (I also like to start with a land factory))
(3.) PGen.|
As soon as it is built start 4 Tech 1 Engineers
(whilst your Engineers are building, repeat and rince this on all starting mine spots with your ACU, but building at least 1 air factory (It is probably best as the second factory TBH))
As soon as the first tech 1 engineer is out have it either go straight to work on reclaiming anything local or go for a Hydrocarbon Power Plant or if non of those are present then build some more PGen's (about 4 (IN A ROW))
When the second Engineer is out I send it out to build a few more ME's that are local.
When the third is out I typically set it to build 2 Anti-Air Turrets.
*Before the fourth is out you will have a couple of factory's built, so start building a T1 scout plane and sending it to your opponents base (if there is more than one then I might build one for each opponent.
Next build T1 attack units and put the factory on repeat and forget about it for the time begin, when you have about 5 out of your door I tend to send them on harass, so straight to any enemy ME's or PGens (they should be targetted second to ME's though) right outside the immediate range of his ACU (obviously you should have scouted these spots)
Keep building factory's with your ACU and pumping out more and more T1 units (if you see them building bombers then build more air factory's and build interceptors) instead of tanks.
Once I have 4 ME's up I upgrade one of them at a time to T2. (You shouldn't run out of metal, but just in case you should micro the pause button to make sure you don't hit bottom with your Mass). You might think that you have a lot of power just before you upgrade to T2, but as soon as you hit the button it will disappear so keep an eye on both.
As soon as your other Engineers have finished I set them building the same as the ACU, but also actively seeking out more mass within reach.
Keep upgrading whilst attacking (DO NOT FORGET!
) and keep adding more PG's using the adjacency bonus till you have a stable point 8+ on your Mass and enough Power. Finally then you can upgrade factories to T2 (with micro).
You might want to put some T1 Point Defence surrounded by walls as T1 units are not able to shoot over them effectively! (especially on chock points!)
If you are getting beat then you need more units or you need to work your way around the back of the oppositions assaults and do some damage to the ME's or PGen's and causing breaks in his offensive line (try exploiting such things with your ACU using it to jump in between the line of offending T1's and destroying them).
ME's and to a lesser extent PGen's are the only real points that count in terms of damage in the early game, so do not bother battling it out head on when you can send a sneak force from behind (or from above!!).
Remember your ACU is essentially an experimental using T1 and T3 weapons to begin with and will wipe the floor with small to medium amounts of T1 units, so use it offensively!
Never give up the offensive as well. I have seen so many replays where the opposition were beat and a few units would have taken them two pieces, but the offence is just stopped to regroup. Regroup behind the front line, but keep the front line in existence (as long as its not his ACU). What I am saying is never give up the offence and keep scouting for breaks in the line or sneak attacks behind your lines (if you see a sneak attack then exploit it!!!)