Start by not drinking any sugar, including juice except perhaps with a meal high in fiber and at to lower the impact.
Limit refined grains, white potatoes and sugar. No cereal, bagels, toast, etc for breakfast, snacks, etc. eat real food.
Remember that Fat and fiber lower the glycemic impact So high gi food or drink should only be eaten in combination with low gi foods and you should only have small amounts.
And to repeat. Eat real food. Vegetables, fish, meat, eggs, fruit, drink teas, water.
The low glycemic diet is the best thing for acne. alternavista is right, instead of cereal every morning try steel cut oats. Not the rolled oats because you really want your body to work for those carbs, but if that's all you have it is better than cereal. Have an apple instead of a banana, apples are really good at balancing out insulin levels. A little trick that works for me is to add something acidic to my food or drink to slow down the gastric emptying. I usually go for lemon juice in my water, I've tried ACV, but that stuff is disgusting and I certainly don't want to lose any more weight. Eat rye or pumpernickel bread instead of whole wheat bread or white bread because from what I read they have a GI in the 40's which is low and that's good. One of the highest GI foods to avoid is white rice and especially jasmine rice. Go for basmati, wild rice, or quinua. Lastly, eat 4-5 small meals at least 2 hours apart instead of 3 big meals this prevents a drastic spike in blood sugar.