I have a few questions I would like to get answered. Thanks in advance!

Should I buy a tub of buttercream or should I make my own?

Also if I wanted to color the buttercream should I buy it already colored and flavored or can I add food coloring? Which brand is recommended?

Thanks

Does anyone recommend a reasonable website where I can purchase all my tools for a good price?

I haven't bought pre-made frosting in a long time and I know nothing about buttercream bought in a tub. I guess it would depend on how good it was and how much you'll really be using it. If you're running a bakery I could see how it would be helpful but if you're just doing a few cakes you're probably better off making your own.
As far as coloring goes, I would color my own because you'd hate to end up with a whole tub full of a color you never use. To color your own you can use gel/paste or powdered food coloring. In small amounts regular grocery store food coloring is fine, but the gels will get you brighter colors without potentially adding too much liquid to your frosting.

I certainly would recommend making your own b'cream. There are sooooooooo many good recipes on this site that you can't go wrong
Color & flavor it yourself so you can get the shades, & flavors you want. If a recipe for icing calls for a flavoring your don't like or can't get it's easy to change it -- flavoring is very much a personal thing
Good luck and happy baking!

I would not buy the store brought verse of icing. I am in the course 2 of the wilton classes and I didn't bring any icing with me. I had to buy the store bought and I'll tell you after about 20 minutes the icing would not hold up for things like borders, flowers and etc.. It starts out stiff but ends up being very thin after using it.