Hmm, it totall depends on what you want. Do you want to write a bot that is an all-in-wonder? You probably start then writing a lot from scratch to make sure the bot is using classes and also is able to work in other mods and such.
If you just want to play around first, i suggest you hack into some existing bot sources.
After that, i'd say:
- work on code structure first
- work on navigation
make sure the 2 above are almost complete. The code structure should be readable, (its hard to keep it readable if you code a lot new stuff) and it should work of course. Then add a simple form of navigation, like using waypoints/nodes/navmeshes/no waypoints (tracelines nav).
once you got a solid code, where you can code from you can expand your bot easier.
In very short order:
code layout/structure
navigation (select goal, make path, walk)
combat (fight, shoot, take cover)
advanced navigation (goals)
advanced combat (flanking, swat behaviour?, outsmart enemy)
fancy stuff
