I think anytime you can get an impact player at 36 you take them. Every draft publication I see has Gibbs going in the teens to the 20's so the odds are that he won't be there. Gibbs doesn't seem to have any redflags other than being short and somewhat on the light size. Still he is almost a sure (high Floor) thing to be a good back and has a chance to be a star. While edge and CB are bigger needs I think you have to pull the trigger if he is there. I might even be reasonable to trade up for him if he falls near the very end of the first round.
Offense needs to be fixed but has a lot of talent already. Adding another big time playmaker sure would make fixing the offense easier.