Creaks from the bb are not that hard to diagnose or fix but you usually have to test the bike under load.

Swap in some pedals you know are 100% and go for a ride...if there is still a creak then it's not the pedals.

Check the chain ring bolts and go for a test ride, if there is a still a creak, it's probably in the bb.

The bb threads should be greased and I always install crank arms without grease. *

Seat posts and saddle clamps can also generate some creaks and squeaks that may seem to be coming from farther down so check those too.

* We could debate the greased vs un-greased spindle thing all day... greasing the spindle is not an issue if the crank is installed properly.