Take a look here
http://www.bowproshop.com/sights.html I have something simular to the 0l 3000. I used a sight like this when I first started that could be had at walmart for 10 bucks, it was made of plastic. I got back into archery again last year and was not happy with the sight I had and want to go back to the basics but the old sight would not fit on the new bow, the cable guide rod was in the way. This is what I picked up or at least something simular. Basically you put tape on the back of the sight and make marks for different ranges. For hunting I leave it on 20 yrds but leave it loose enough, it can be moved up if needed.
As far as your sight settings, if you are shooting any kinda of speed at all you will have the same point of aim at 20yrds as you do 10yrds and 15 yrds. I have always had 5 pin sights at least besides the two listed above. I kept a 20, 30, 40, and 50 yrd pin as I use to shoot 3-d and 50yrds was the longest shot allowed by the rules. I either removed the 5th pin or put in as low as it would go. It served two purposes for me there. One was for playing around at 75-100 yrds depending on the setup, I tested to see what range it was set at, this was for playing around or shooting at some of the prize shoots where they would have a little one inch red dot on a small target like a woodchuck at around 100yrds and first to hit it wins the prize ( I never won). Two it also served as my very close range sight. Sometimes they would put the small targets like mentioned above in very close like 3-5 yrds on the course. If you shot with you 20yrd pin you would hit it the top of the target or shoot over so using a pin closer to your arrow would keep you in the 10 ring.
If you use the 3 pin do 20, 30 and 40. I use the 40 yrd pin for practice mostly, it makes you a better shot up close.
Now say you want to shoot 25 yrds, center you peep between the 20 and 30 pins and line up on target and fire away. I do it a little different though, I think it is from starting with the type of sight I did. I line up center on the 30 pin looking through the peep but hold on target where I want to hit at 25 between the two. At that range it did not matter much for me but found I was more accurate when shooting longer shots like 47 yrds where you are not dead center between two pins. The trick is do what works for you. I have known a guy that did 15, 25, and 35 yard pins but that would confuse me.
I prefer the one pin sight, I do not have to think at full draw which pin I need. With some practice you will be able to tell where to hold if the target moves on you at full draw say from 20 to 25 and you are set on 20 yrds. This would bother some thou so it may not be for you. I am not trying to push you on this sight, I am just showing you one more option and how most people set up3 and 5 pin sights.
One last thing to look in to, if you get the bow with a 3 pin sight but want a 5 pin sight many sights you can buy and add pins to if there is room for them.
