So, apparently the skyrim game guide is useless for telling you how much gold vendors have.

Does anyone know which vendor has the most gold?

Whichever one you want; buy from only two weapons venders (except for rare occassions) and never sell to him/her, but to everyone else (get the perk where you can sell anything to anyone, it will help). The more you sell to a vendor, the less gold they will have in the future; just like how the more you buy from them results in them having more gold for in the future. Just need to be smart about it.