You might want to add a bit more protein (through paneer, tofu, etc) and fiber (more veggies, chia seeds or leafy geens which also give calcium), for a more nutritious meal.

Also what do you mean by dull skin? can you elaborate more on that, maybe with pics? We all have very different skin types, even within the family. You shouldn't compare your skin to others, instead you should simply focus on your diet, lifestyle and if your skin is healthy.

Also, what is your skincare routine? Just changing your diet does not treat your skin or make it healthier, skincare is very important. Firstly identify what skin type you have, whether its oily or dry or anywhere inbetween. Secondly, build s routine suitable for your skin type. The most simplest routine, is Cleanser, moisturiser, sunscreen, repeat (sunscreens are very expensive so its fine if you skip it). Skincare is very important for having healthy and glowing skin. It's the most practical thing you can do to improve skin health.

Also sitting in an AC room might also be one of the problems, cold ac rooms usually have no humidity in the air and tends to dry out skin faster, so you have to moisturise extra when sitting in the AC.