How tall r u ?
123 shd be fine for ur age.
Diet is 80% and exercise is 20%. If you don't have time to workout then work on eating better. Eat a lot less sugar and cut out simple carbs. Eat more veggies and some protein. Best to prepare your own meals versus eating out. You don't know what other people add to foods. And you do have time to workout, do HIIT workouts like bodyrock.tv
Dukan diet worked for me out of all the diets I tried. You don't have much to lose I think this would be perfect :)