Quick input from a newb... It depends on your playstyle, in all honesty. If you jump on, unload, then don't get back for 2-3 hrs, CoE is best... More hits. If you play a lot and are active for hours on end, CF/TL mix isn't bad for plunder. (._. ) Crawls back in hole.
Builds doesn't matter much. Jus hav reasonable spy stats and stay active. Hit a few more times by being more active and it covers whatever other builds is said to offer