Because no one linked it:
http://www.invokergame.com/
Just knowing what the combos are doesn't help you if you can't quickly switch from one spell to the next on the fly. It needs to be muscle memory, or close to.
Past that, basics: Forge spirits melt armor and can tank towers (and don't rush 4E/4Q for two spirits, that's what noobs do). Cold snap for stuns, especially chasing. EMPnado is your setup. Remember that what effects what, don't use a meatball with one level in exort and max Wex (wex is range, exort is damage). QQWalk is your panic button. Alacrity yourself if you're going right click invoker, otherwise just put it on your spookiest ally (think of it as ogre magi's bloodlust) it also can be cast on siege creeps for some additional conditional utility. Ice Wall's damage is shit, but the slow can be badass; only use Ice Wall if you have a lot of quas for the slow, if you're exort-based it won't slow them for shit and will be a waste of mana. Sun strike's relatively straightforward, but one interesting thing people miss: It's your only spell (other than alacrity) that isn't blocked by BKB. Even the forge spirits' armor melting is blocked by BKB, but sun strike ain't.