

Economic superiority is the single best advantage you can have over other players, especially if they're human. At the very least, capture your 'half' (or equivalent, in the case of 3+ player matches) of the map as early as reasonably possible. Most maps have a vast amount of mass deposits available, and if you turtle up early and neglect expansion to these mass spots, you are giving your opponent a massive economical advantage, meaning more hostile units, more hostile upgrades, and more hostile expansion. Furthermore, you cannot harass your enemy effectively without, at least, a small assault force to attack them with, which brings us to our next point: Mobile combat units are vastly more useful than static defense buildings, and early-game ACUs are too slow to be used for expansion. That said, there are specific guidelines that can make your life much easier when contemplating what to construct: Because of the flexible nature of RTS games, there is no single pattern to follow when building. At a whopping $1.24 before taxes on the frequent 75% sale, it's a bargain bin of content.
SUPREME COMMANDER 2 UNITS 56K WARNING FULL
For the full experience, I strongly recommend investing in the Battle Pack. You'll feel it within minutes of starting a match.
SUPREME COMMANDER 2 UNITS 56K WARNING SERIES
This breaks the longstanding tradition of the Supreme Commander series that mass should be taken and held for any period of time possible (as they tended to pay for themselves rather quickly and never became more efficient), and more of a long-term investment that should be prioritized more heavily for destruction and more heavily for protection. What this means is: With the DLC enabled, holding mass extractors for long periods of time becomes enormously more important. The difference is simple: with the Infinite War Battle Pack 1 DLC enabled, mass extractors run at 50% efficiency after being built and scale up to 200% efficiency over time (roughly 20 minutes after being built).

The relevant DLC can be found here and is, in this author's modest opinion, completely worth the money. The first thing to know about this game is that there is a distinct difference in the game's economy in a game that is DLC-enabled vs. Note that this section does not apply to tutorial or campaign missions.
