Assuming your bow fits your draw length, have someone mark your arrow, about 1/2" forward of your rest when you are at full draw (obviously this is best done from the side). Then measure from the mark to the throat of the nock. That's your arrow length. Then get your arrows cut to that length. No reason to be shooting a few extra inches of arrow.

Once your arrows are the correct length you can think about spine and tuning. I recommend walk-back tuning, and then broadhead tuning. There are threads on these methods in the Technical Forum, and they are relatively simple. Make rest and nockpoint adjustments according to what the arrows are telling you (not some preconceived notion of what "centershot" must be).

Good luck!