More specifically, you play king's court. You then may choose an action card from your hand to play three times. You choose nobles.
So you play Nobles three times.
The first time you play Nobles, you choose, and you can either get +3 cards (meaning you draw 3 cards) or +2 actions (which means that you get the ability to at some point in your action phase this turn, play more action cards; it does NOT mean that you just play those actions immediately, or that you have to play any actions at all, or that you gain action cards. It seems to me that your confusion is because you don't really have the firm understanding of what +2 actions means).
Then, the next thing you do is play that same Nobles again. You make the choice again, though you can make a different choice this time.
Then you play the (same) Nobles the third time. You again get a choice to get +3 cards or +2 actions, and to emphasize again, the choice is totally independent of what choices you made on the first two plays of the Nobles.
AFTER all of that is done, you continue with your action phase; if you have actions left to use and action cards in your hand to play, you may play them (though you don't HAVE to); you can also proceed at this point (or after playing and resolving any subsequent action card) to your buy phase, after which you won't be able to play any more actions, but you will be able to play treasures and buy a card (or more than one card, if you have played a card which gives +buy).
I hope this makes things clear.