vitamin supplements for teens?

to improve my performance in school i wanted to take some vitamin supplements

i was planning on taking
magnesium 150 mg
vitamin E 250 IU
Vitamin C 250 mg
B1 (Thiamine) 15 mg
B2 (Riboflavin) 10 mg
B6 (Pyridamine) 5 mg
Folic Acid 200 micrograms
B12 - 50 micrograms

If it would help I have my average day's food below:
B
1 Bowl Cheerios, 2 egg whites
L
2 PBJ sandwiches, nuts, yogurt
S
Apple or bannana, nuts
D
Meat (I usually have 2 1/2 card decks worth), salad, carrots, potatoes
I was going to take a regular centrum multivitamin along with that (but if you compare the numbers the multivitamin in insignificant). I checked some statistics on the safety threshhold of these vitamins (the level where there have been no reputable reported cases of harm) and the amounts I have are significantly below).

Is taking a lot of certain vitamins in proportion to others bad (would that cause an imbalance)?
Also, should I alter any of the amounts?
How often should I take them