I think the 12 and a half is a must. The Omnigrip(the green ones) are the best. They really are less likely to slip when you are using them. You can cut most things with just one good ruler like this. A lot of blocks are 12 and a half unfinished, so I would start with this one and buy others when you figure out what you really need or will tend to use most often. I have inherited a few I have yet to use and I don't have a big selection of them.