Gingivitis is reversible if you brush after every meal, floss two times
a day, and get your teeth cleaned every 3-6 months at the dentist. I'd
reccommend getting an appointment pronto.  They'll x-ray for cavities
or signs of bone loss and check your gums for signs of gum disease. My
gums were bleeding a little and inflamed, but the dentist told me after
the cleaning, if I used better technique brushing and flossed everyday,
the gingivitis should get better in three weeks.

Gingivitis is the first stage of gum dsease. Like I said, it's
reversible. If they x-ray and notice signs of bone loss, that means you
have periodontitis, which is what my father has and it's irreversible.
You can continue brushing and flossing to keep it under control. And
remember, don't brush too hard and use a small soft bristle toothbrush.
Try brushing the visible parts of your teeth, the parts where you chew,
behind and the sides of the teeth. And gently brush the gums a little
as well.

If you have gingivitis you might notice some areas of your gums are
inflamed or sensitive or bleed when you brush or floss. If you rarely
floss and start doing it one day and they bleed, don't worry. That's
normal. Just keep flossing and the gums will "toughen" eventually.
That's not a sign of gingivitis. :)

The only way to get rid of tartar buildup is to get them professionally
cleaned at the dentist. Use Colgate tartar control toothpaste for now
on.

And I reccommend multivitamins unless you -know- you are lacking
vitamin C.

Anyway, these are the steps to stronger teeth:
1. Avoid sugar and sticky foods that get stuck in your teeth.
2. Drink water over other liquids, especially liquids with sugar like
soda or juice. If you want to avoid stains, avoid red wine, soda,
coffee, and dark tea like the plague. Not only does water help your
teeth, it helps you feel hydrated and fresh and helps people lose
weight. So drink up.
3. While eating, take a sip of water every few bites or so and swish
the water around in your mouth. It'll remove some food particles if you
can't brush right away.
4. But try to brush and floss immediately after eating.
5. A lot of articles on dieting say eating six small meals a day helps
people lose weight, but it's actually smarter to eat three big meals
(healthy, mind you) and eat the snack immediately afterwards. They say
you're less likely to get cavities if you eat a bag of candy in one
sitting and brush your teeth instead of eating a few pieces every few
hours because you're less likely to brush your teeth after eating a few
pieces every few hours. That would be too much brushing if you did...
6. Some people say Listerine is "blah", but my dentist says it's the
best mouthwash out there. Swish it in your mouth for thirty seconds
after brushing before going to bed. It says it reduces gingivitis with
good oral hygiene. Better safe than sorry, I say. Just don't use it too
much because it can dry your mouth.
7. Just eat healthy! Avoid sticky foods and try eating more vegetables
and fruits and meats. Drink milk or eat some cheese if you're not too
big on milk. And if you have to eat sugary foods, eat it every blue
moon. And I'd personally avoid sticky foods altogether.