I would work on proper deck construction if I were you Shanna. Constructed decks (pre-made decks, not opened on the spot) typically have a minimum card limit of 60 with no max. This means that most people will run EXACTLY 60 cards because for every card over this you drastically decrease your odds of drawing relevant spells. With this in mind, you are allowed 4 copies of each non-basicland card in your deck. So naturally most decklists you will find will also be running 4 of all of their best spells. Here's a friends deck as an example:
http://www.wizards.com/Magic/Digital.../tourn/2803260
As you see, his deck (the top one) is running mostly 4x and 3x all of their spells in order to best increase their odds of seeing them. Another thing to note is his land count of 23. Just starting you should probably run 24 in all of your 60 card decks as a general practice until you get better at calculating the math needed to figure out exactly how many you really need. Decks made of cards that have a lower converted mana cost (CC) tend to run fewer lands, while decks with higher CC will run more naturally, but with 24 you should be seeing enough regularly in your games so that you're not "mana-screwed". One last basica thing to keep track of, regarding lands and CC; pay attention to how many cards in your deck are expensive/cheap, so you can start making mana adjustments accordingly.
As far as colors go, no color is really "stronger" than any of the others as in it will outright win, that said the colors generally have particular effects that show up repeatidly within them. They are as follows:
blue - permission/card advantage
green - big creatures
black - removal spells, zombies, death, sacrifices, regeneration etc.
red - direct damage, haste creatures
white - protection, powerful enchantments, solid creatures
Some colors power well together, although with the depth of the cardpool nearly anything can be concocted and work out fairly well.
First 60 card deck outline:
23-24 lands
8 removal spells (kill your opponents creatures)
20 creatures
8 fun spells/enchantments to play around with
Have fun!
EDIT: Also, you may want to try to avoid "color screw" (not getting the proper kind of mana, by running either 1 or 2 colors, although with a high land count and some filtering you should have little difficulty splashing for a third if you wish.