As a general rule, I'd strongly recommend against starting with a collection of general-purpose routines; they will often do much more work than is actually necessary for a given application, wasting cycles and RAM.
Start with the game concept, and sketch out the design. For all data structures- including number representations- look at the ways your game will use them, and choose representations which make those operations easy.
An efficient program will flow from appropriate choices of data layout and structure. Different design constraints ask for different representations.