Hey good luck. I'm in the same boat. I've gained a ridiculous amount of weight over the last few months and I'm dying to get it off. I used to be such a hot little thing 3 years ago.
I skyrocketed to 150, and I'm 5'1 with a petite frame. Nothing fits me anymore and I refuse to go clothes shopping for things that will fit at this size.
I will be happy if I can get down to 130, but ultimately, I'd rather go back to being 110-115 as I loved the way my body looked at that weight. I was exercising a lot too. My normal weight, according to BMI, is approximately between 95-130, so I'd prefer to be less than 130...but it's a decent initial goal I suppose.