Well, if you are going 1v1, you want to harrass your opponent while you get gauss. I used to do this build order:
R > Hog > SP > SP ( go collect minerals and as soon as your reactor is complete, get the first upgrade)
SP > Hog > Hog ( keep on collecting minerals and go scout your opponents. you should have 4 to 5 hogs under 2:30 minutes. Around this time, go harrass your opponent's 4th or 5th building. if he has nothing than you can research two more hogs and wait for grenadier. If he puts a fight or he got turrets, go back and collect minerals while you put your second reactor up. get the second upgrade and then
Hog > Hog > Hog ( kill neutral bases and recycle you 3rd supply pad. build your 3rd reactor there and get gauss cannon upgrade. get one more base and go attack. research more hogs while you are at it. You will get gauss but it won't be the fastest way. But this is one of the safest ways to get it if you are playing 1v1. Oh and don't for get to upgrade your two supply pads.
if you are on a team game: 2v2 or 3v3 follow this order.
SP > SP > Hog > Hog > Hog > Hog ( go collect minerals. by the time your last SP is complete, you will have enough resources for your 1st reactor, so...)
R > Hog > Hog ( Research the first upgrade and upgrade your pads. go destroy neutral bases)
SP > R (build your 3rd SP and your second reactor. dont get hogs. wait for the grenadier upgrade. recycle your 3rd SP and build your 3rd reactor. research gauss and recycle your 3rd reactor. get two more bases and build one at least one SP on each. Start pumping out hogs like crazy. you might want to build a VD or an AF. Always have at least 3 bases in total. Go around just hit and running everything. keep on pumping hogs and upgrading your supply pads.
Here is the build order.
SP > SP > Hog > Hog > Hog > Hog > R > Hog > Hog > SP > R > recycle SP > R > recycle 3rd R > VD/AF
you should have about 7 to 8 gauss hogs in about 5 to 6 minutes. One you get your second base and you are waiting on gauss, start pumping hogs from there. Each map is different so if you have enough to purchase a base in the early stages, you can get more hogs with gauss in 5 minutes. if you are having trouble with it. send me a request to Lunatik101 and I can help you further.
Ronin 3003:Practice raging tanks in private games. If you can't rage full pop tanks w/ a T1 arby, it means you are worse than klunk and should consider using a different leader. =/