Here is a table for build orders for different teams on different maps:
Maps with Ore: Small Power, Small Power, Barracks, Ore Refinery, War Factory, Ore Refinery, War Factory, Ore Refinery, War Factory, War Factory and use the $3,000 rule as seen above. Build an ore truck when u get your 1st war and when you get your third war.
Maps with Ore: Small Power, Barracks, Ore Refinery, War Factory, Ore Refinery, War Factory, Advanced Power, Tesla then use the $3,000 rule.
Allies (Germany, England, France)--
Maps with Gems: Small Power, Barracks, Ore Refinery, War Factory, War Factory, Advanced Power, War Factory, service depot, Ore Refinery; From then on build enough power to stay out of low power, war factories if you have over $3,000, and ore refineries if you have below $3,000. Build an ore truck when you get your third war and build about 5 MCV's when u get your service depot. The rest Tanks.
Soviets (Russia, Ukraine)
Maps With Gems: Small Power, Barracks, Ore Refinery, War Factory, War Factory, Advanced Power, War Factory, Service Depot, Ore Refinery, War Factory, Ore Refinery. When you get your service depot build MCV's then tanks and alternate. After you get about 5 CY's build power then start building out of your base towards theirs. If they rush build teslas.
These are the Basic Build Orders for the different teams. As you progress in skill you will be able to come up with different strategies for different teams.