There is no "always use this startegy"
With that in mind, always build up a good economy. unless you prefer losing.
AI CAN build buildings, but it takes some time before they get started and when they build, its usually more levels of IC.
Always stay agressive. Attack AI for more resources and the eventual VP you are gonna need to win and attack players to beat them. Best to attack them before they attack you. But dont rush in headlessly. Be ready, be prepared to lose some units, thats OK, as long as the other guys loses more and in the end, loses them all.
Many people will fight me on this. All you need is Light tanks and bombers. Unless the game runs a bit long. 1-2 months.
Then you also need some AT, AA, Artillery and Interceptors. (in some cases you also need a navy, but mostly you can settle for destroyers and subs.
Many people will whine and moan about rockets. "oh rockets are so cool" They are expensive. They are slow and when you have actually payed for the research and the build, then you have top pay an expensive upkeep while they are moving SLOWLY from airbase to airbase, always getting there late, since your many bombers and light tanks have already fixed whatever problem there was, when it gets into range. Then you have to move again, still paying upkeep.
As for Nukes. If you are letting your enemy build these, then you are doing it wrong. You should have won most games before nukes are able to be fired. Should a game run long, keep an eye out for power plants and kill them before they start building problems. Use spies, bombers, arty or just take the province. Anything to stop the nukes. (can be a bit though in a 100 map when guys on the otherside of the planet are building them
)
Some maps are different though. Take the Antartica map.
You will never need any navy.
You will need all land units, with a few exceptions. No need for heavy tanks or militia (never build militia in any game (unless you play Tibet, Mongolia or some other militia nation)
But here you are gonna have the economy for it, its so full of resources that you can fumble your way through the game.....mostly. But mainly, light tanks and tacΒ΄s.
Now, all this should, ofcourse, be modified with skill when you get into a fight with a skilled player. The game is different and better when you have to struggle, think and do your best.
Hey, look at me, I used the forum, how 90Β΄s of me 
Good luck with your games.

