I'm new at this as well. A couple tips that I've found to help with my shot a lot:
Keep your weight more on the balls of your feet, knees slightly bent.
Focus your draw on your back muscles, between your shoulder blades.
Your draw arm should be an extension of your arrows, going straight back behind it (elbow in alignment).
Perhaps most importantly, and noticeable in making my shots better: push the bow towards the target slightly as you release (let your fingers relax and the string push them away). Keep aiming; don't drop your arm until the arrow hits.
You can feel it immediately as a good shot when you follow through with good form...and bam, the arrow goes right where you want. Well, every once in a while, anyway.
As far as arrows go, I've lost a dozen already. I have yet to damage any carbons, but ruined plenty of fletching by shooting into the ground. In general, don't get anything too fancy. Seems like carbon is the way to fly.