Schedule will depend on the dragon's age, so that would be important to know. I have used Rep Cal Multivitamin for years, and that one still is a good choice. Recently, I have been trying Repashy Calcium Plus. This is of course calcium with all the multi vits to include D3. It really depends on choice. As I had an egg laying female and a baby dragon, I figured the extra calcium would not hurt.
Either of these choices will be fine and dosage schedule is dependent on age. For dragons a year old and under I dose multi vit 2-3 times per week, and for adults once per week.