Coinmaster is a very basic detector, it was my first and I still use it for club hunts and do really well because at club hunts you dig everything and it's all very shallow.
Since you don't have anything to compare it to I'm going to lay out the difference between Coinmaster and a 0-99 metered machine.
There is only 1 trick, and it's the same trick with a lot of detectors but the Coinmaster screen is to simple to see the really good positive hits so it's harder for your mind to comprehend junk like on a 0-99 VDI meter. If it is jumping around at all, especially jumping onto something you think is good, then up to the 50 cent piece and all the way over to iron then it's junk.
On a 0-99 VDI meter detector you will see a solid coin hit be say, an 81. You go over and over the target and it may drift to like 82 occasionally. You would definitely dig that. If the target was junk on that detector you would know right away because it might say 81, but it will also be jumping to 13, 99, 45 and back to 81 etc. You know it's junk. You can't see that effect nearly as well on Coinmaster.
If you are dissatisfied with the Coinmaster don't give up, just understand it is very limited. You might be happier jumping into a better detector like a White's MXT, AT Pro, Minelab X-Terra 705. Or maybe just trading it in for a $199 Fisher F2 with a meter so you can see the other type of display.