Don't use margarine, use butter. Vitamin D milk rather than 2%. Other than that, make a lot of high-cal smoothies and shakes: ice cream with heavy cream, Oreos, yogurt, vanilla, etc. to sate your sweet tooth.

But, don't neglect your veggies. If you just cut those out, you'll throw your gut bacteria out of whack, and you won't be able to digest the calories as efficiently, and your gain won't be as effective--essentially, you'll retain a lot of water, and if you stop for any amount of time, you'll lose a lot because that water weight will absorb into your body.