0.5 mm is what you need for small writing, fine drawing and graphing. yeah you break some leads but it's worth it. 0.7 mm is better for everyday writing. choose your lead hardness for either.
I started off using Pentel PD365's. the blue one exclusively through 4 years of college. that one pencil.
I quit using PD365's the day I discovered P205's. they are the ultimate. Office Max makes an exact clone.
the Zebra M-304 would be my next choice but they are a bit too small. probably better for people with small hands or packing in your briefcase or glovebox.
the Bic cheapos are good everyday pencils that can get lost. they work just fine.
the 0.7 mm twisties make good lumber pencils if you can get the hang of it. hard to break, tough body, and last forever. I think these are from the 70's.
Office Max makes these erase-o-pencils that work fantastic and refills are cheap.