A few quick tips I have thought of that may assist you when playing Ladder games.
1. You NEED to know what's in all of the races so you can create a counter against a certain unit, because it would be unwise to send an archer against an abomination.
2. If you are going to rush, never go into Low Upkeep. Keep your food at about 40-50.
3. Watch the replays of pro's, or watch people playing in a custom game. You need a good building strategy. You also need to know the terms "Micro" and "Macro". For all those who do NOT know, Micro is the control of one or more units at a certain time and Macro is the position of you're buildings. Macro is helpful because it can block out harassers.
4. As I said in 1., you need to know what is in all of the races! It is a must. You also need to know the abilities.
I hope these tips do manage to help you out in future gameplay.
why yes i suppose it wouldn't be wise to send t1 against t3, thank you for your insightful tips.