I'd like to point out that there are more than a few people who take the game far too seriously. 
That said, play the game, try different things out, and read the strategy forums for some ideas.
Now a few notes that may help you out. Please bear with me if they seem overly pedantic and/or useless.
This isn't really an RTS. It's more like a Diablo Arena or a third person CounterStrike or Team Fortress. With half of the Demigods, you only control your own character. With the Generals, there are strong builds that don't depend on the Minions.
If you read the manual, you probably understand the commands. However, here is a quick run down of the first few clicks you should do. Click on the Plus sign to the lower left of the Demigod portrait. You'll be taken to a screen to select where to put your first point. Second, you may want to click on the forth circle on the right side of the bar. This will open the favor item area to select your favor item for the game. You can't change the item during play. Check some of the forums for a basic ranking of items and why. Click on the shop and choose items. The cursor changes to a coin over a shop type structure.
In the beginning of a match you have chosen a Demigod with their own unique starting stats and abilities. Depending on your play style, you first buy some equipment. Then you go to kill some creeps. The basic idea at the beginning of the game is to kill creeps and avoid dying. There are usually multiple paths of creeps in the game called lanes. I'd find a lane without another Demigod in it and just stay there killing creeps. Most lanes have a flag in the vicinity, stay near it to capture the flag. You'll get a boost to xp plus whatever abiltiy the flag possesses. If you get attacked 2v1, run. Don't just run to the towers, run deep into your territory. If you're really low, run to the green crystal in your base.
If they look to be camping the creeps or capturing the flag, like you should be doing; go to another lane, help a team mate, or if you have a enough gold, run back to base and buy better gear.
Good stuff to get: There is a great ITEMZ guide in the strat section of the forums.
A random fact, you can drop your stuff. Don't right click on your items and gear. You'll drop the item and other people can click on them to pick them up. That said, when team play picks up, keep an eye out for gear that other people may have dropped. OR, help a team mate out by dropping potions, scrolls or other items for them to pick up/use.
Second random fact, there is an aggressive move function. Alt click the ground and your attack the first thing you come to. However, a quick tip is that there is more gold and xp in the archers and priests than the grunts. If you click on them first you'll speed your leveling and gold income.
Stardock Forums
Demigod Forums
That said, play the game, try different things out, and read the strategy forums for some ideas.