For a good multi-vitamin, I consider the minimum to be at least 25 milligrams of each of the main Bs (B-1, B-2, B-6, e.g.). I also consider more to be better as far as the water-soluble vitamins go (the Bs, vitamin C, and some others are water-soluble, while A, D, E, and K are fat soluble).
'Bear in mind that the RDI (recommended daily intake), DV (daily value), or whatever, is calculated to be the dose that keeps you from overtly DYING of a nutrient deficiency.