A healthy diet definitely starts with the right breakfast when you have gestational diabetes. Because your blood sugar levels tend to be low in the morning when you get up, you need to take special care that your breakfast is appropriate. A meal that is high in protein and includes complex carbohydrates is ideal. Think of boiled eggs, some meat, beans, a slice of wholemeal toast... Just make sure your meal is not too large.
Many diabetics benefit from a small snack between breakfast and lunch. Waiting too long between meals causes blood sugar issues, so some fruit, carrot sticks, or wholemeal crackers with a nice spread could be great for you.
For lunch, proteins should play an important role again, and vegetables and carbs should be included in your lunch. Wholemeal pasta with vegetables and some meat is a great option, for example. After that, rinse and repeat the snack suggestion given in the last paragraph, because your blood sugar levels could dip if you wait too long between lunch and dinner too. A chicken salad with lots of vegetables and a nice dressing makes for a great meal. You could combine this with wholemeal tortillas to create wraps, or eat it with brown rice. You could also make a cold rice salad with nuts and raisins. It's important to keep trans fats out of your diet. Once your dinner is finished you might another snack later in the evening, again to keep your blood sugar levels up. Also see, what to expect from a glucose test?