B VITAMINS KEEP YOU HAPPY AND COHERENT. more info http://archure.net/salus/bhappy.html
GOOD BRANDS  a good brand should have 100 mg of each. Dr Shari Lieberman http://drshari.net/says 25mg to 300 mg /day
100 mg of B1 (Thiamine) boosts immune system and energy level
100 mg of B2 (Riboflavin) restores body and brain with new cells
100 mg of B3 (Niacin flushes you red and cleans veins OR Niacinamide does not flush nor clean not as good as Niacin)
100 mg of B6 (Pyridoxine) cures and prevents depression, helps manage serotonin
100 mcg of B12 (Cobalamin) helps mental/physical coordination
(as well as other B agents: Folic Acid, Biotin, Choline, etc)

Typically Labeled as:  "Vitamin B Complex", "B Stress Formula", "B 1000", "B 50", "B 100"
Synthetic Vitamins are cheaper and are just as good as Natural Vitamins (as per Durk Pearson and Sandy Shaw book "Life Extension").

5-HTP 100 mg: I would also get some "5-HTP" 100 mg/daily. I take 100 mg daily, it provides "Serotonin" aka "neuro-transmitters" needed for thought process and transference of information within the brain, more depth of thought and better utilization of the mind. Lack of "Serotonin" aka "neurotransmitters" is the reason that people become confused or even angered (when the world behaves like they do). More about "5-HTP" http://www.archure.net/psychology/mentalhealth.html

B VITAMINS with NO VITAMIN C: Do not get a B Complex or B Stress if it also contains Vitamin C. The reason: You can easily take up to 1000 mg of B Vitamins. B Vitamins are typically 100 mg, so thats 10 tablets or caps, but if you were to take 10 times the Vitamin C, it could be an overdose of Vitamin C (1000 mg, ok for a cold, but daily 500 mg). Vitamin B6 (Pyridoxine) overdose level is 2000 mg/day (can cause temporary nerve damage in the extermities, aka feet/hands)

A multi vitamin / mineral is better than nothing. It will keep you alive, having the bare minimum required for life, but most multi-vitamins typically do not have enough B Vitamins to keep you Happy. Over 50% of people don't take any vitamins. /// AND /// People who do not take vitamins do not get enough B vitamins from foods. More info and links http://archure.net/salus/bhappy.html
ALSO: get an additional B12 vitamin, at least 1,000 mcg (grocery stores) or 2,500-5,000 mcg (vitamin stores) helps mental/physical coordination. I take 25,000 mcg of B12 per day; AND essential "5-HTP" 100 mg/day provides Serotonin for the brain, cures confusion and anger, helps the mind function deeper on more levels. Here in Las Vegas many stores are 24/7, grocery, pharmacy, large stores, small corner stores, anyplace that would sell food and vitamins, and generally have these in stock
BETTER BUY?   Any grocery store or pharmacy where vitamins are sold. Any brand name. Some may be initially cheaper, but often the dosage is much smaller, thus it may not be the better buy.  You will have to compare and estimate.  60 tabs of 25 mg for $5.50???, or 50 tabs of 100 mg for $11.00??? (the later being the better buy).  
INSTRUCTIONS: You can take them with a glass of water (admittedly, they taste kind of "gaggy", but they sure do make you Happy, within 30 Minutes), and you can take them with a meal or on an empty stomach.  (Better to take them with Water than coffee or soda, just to get them down the throat, as coffee and soda are both acidic, and water is just easier). 
IF YOU HAVE NOT HAD B SUPPLEMENTS DAILY for a while, I would advise taking 600 mg per day for at least 2 days, just to get you back in the pink.  WARNING: if you have been low on your B Vitamins and suddenly take a large dosage, you may experience convulsions of laughter (you'll get over it).  
I met an RN (Regestered Nurse) and asked how many milligrams (mg) of B Vitamins she consumed per day, she said 1,000 mg, I laughed and she said "but I need to" (with all the good work she does, good for her). 1,000 mg /day is safe.

This page, courtesy of www.ARCHURE.net