Respin and Gambling
One thing that could alleviate this problem is to revert back to having the actual skill displayed instead of a skill book chest so players are sure of what skill they are getting.
However, my main suggestion is that when you spin and respin, you can't land on the same item twice. That way, each time you respin, you narrow down the field and you have a higher chance to land the item you want, and eventually, it's the only item left.
If I could be certain that I was getting a wanted item, I would gladly buy the coins.
If I had a nickel every time I used respin and I landed on the same couple of items over and over...
I've already spent around $50 and I enjoy the game and will continue to play. But some of us won't pay that much for a "chance" to get the items we want.