Don't forget GPGnet has tons of replays too in the replay vault. Do a search for Sir_Loui replays. You need to change the filetype to .SCFAReplay though since GPGnet saves them as .SupremeCommanderReplay which won't load in FA or vanilla SupCom. Most of the replays on there are from FA though.
There's serveral ways to play the game though. If you want to play online in ranked games you need to learn a very agressive playstyle involving building lots of factories and lots of units, getting control of the map, and only teching up when it's either necessary or you have spare resources. If you're not bothered about ranked play you can play how you want, either agressive, turtling (building secure defences before attacking) or teching up. You can even use the no-rush option to give you some breathing space. Which ever way you play you need to have an efficient economy though.
Some pointers for early game build order - land factory first (as soon as it's building queue up say 2 scouts and 5 engineers), then 2 power stations, then your first two mass extractors, then as your engineers come online send them out to claim the other mass points. Repeat that until you have 4-6 land factories and 1-2 air factories.
Pick a side and learn their units. If you favour defensive play pick the UEF since the fatboy is the best land defence unit (when backed up with radar) and they have the tech 3 point defence. Then you just need lots of T3 AA and T3 fighters and the AI shouldn't be able to touch you. You also need intel on what the enemy is doing as often as possible so you can plan ahead.
You should also think about limiting the enemies economy by destroying his mass extractors and engineers regularly.
