Your dad should have everything he needs, and you are still in school so he should not have much money. Even if he has money, it must be given by your parents.
The best gift is not something you can buy with money. It can be something you make yourself or something you say or do. Only children should be princesses. If you unexpectedly cook a sumptuous meal for your dad on his birthday, your dad will be moved and surprised. He will be moved that his daughter has grown up and knows how to be considerate and has not forgotten his father's birthday. He will be surprised that the princess at home can actually cook.
Another gift you can buy is a health bracelet for your dad. It can resist radiation and relieve fatigue. It is practical and beautiful to give to a busy father. It is also very good to customize a box of exquisite blessing chocolates. These are not expensive and are very suitable for you.