Starcraft isn't something that numbers can teach you. Most people try to swamp up the whole affair with the 12 racks into gas, 13 fact... and so forth. Although these builds work, my favorite is the 1 1 1 build, you have to at least experience the game for yourself before you are able to decipher what is best for you. So To begins I would advise playing with the comp a few rounds and getting to know the basics such as the hot keys and several Micro tricks. As well as master Macro!!
Macro is probably one of the most important elements in starcraft, i would even dare to say more so than micro, because it doesn't matter how good you can maneuver units if the opponent just plain out masses you in every sense of the word. I would say never let your bank exceed 300 unless you have a plan in mind such as expanding or etc. After that you need to know how to multltask. Seriously, never stop producing harvesters, unless you catch wind of the opponent making a move then just produce battling units.
If you are in the middle of a battle and not making units if the enemy wins then their army is gonna kill you, plain and simple. To be able to battle and work things at home. (Like expand, raise another army for backup if you win or defense if you lose the fight.)
Lol I could go on all day but i wont and that should give any noob a decent startin point...