I have found a lube that works great on my road bike, can't comment on mtb off road, and is not overly expensive.
It is called CRC Industries, ultra-light 3-36. It's a dry film lube that is nontoxic, smells good and has yet to let me down! I spray it on after a ride untill my chain is soaked, then blot the excess by running the chain over a dry papertowel. Some times I do this 2 or three times to realy clean the chain. I use it on the cables, brake pivots, deraler bearings, well just anything that moves!
It has not let any part of my bike rust, although I don't ride in pouring rain if I can help it, or get dry on a ride. It takes a lot longer to dry out than some bike products. I tried Raceday and White Lightning and hate them, due to the build up on my bike, and they clumped up on me unless I kept them very warm. Matter of fact the best use I have found for Raceday is for lead pellet lube for my air rifle!
If you find some of this give it a try!