Hi and welcome. There is a lot of diet advice around these forums and the site, but in general have a diet low in carbs and higher in proteins, fats, veg and non-tropical fruit. For snacks, nuts, berries and cheese are always good.
Have you seen a dietician @Talia89 ? Are you testing your blood sugar?
Snacks would depend on what advice the dietician or midwife has given you. It's a balance between keeping your blood sugar controlled and getting good nutrition for the baby.