How many vials of sculptra would I need to fill out my hip dips? (photos)

Definitely, hip dips needs many vials, it all depends on the body as well. Sculptra is a collagen stimulating filler who can achieve augmentation in the area where its placed it requires several vials, and you must place them every 30 to 45 days,  the results last over 3 years and you will find they are progressive so you need to compare and evaluate every follow up to know how many vials you will need in every session. There is nothing better than a surgical bbl, if thats not an option then you need to do a good plan and follow up with your doctor to achieve your desired results 

Hip dips (scientifically known as trochanteric depressions) are basically inward curves on the outer, upper thighs, just below the hip bone due to a space between the hip bone and the thigh bone.
Hip dips are a part of your normal bone structure, and while you can enhance your body shape through exercise and diet,  they won’t make them completely go away as you cannot change your bone structure.
Apart from dieting and exercising, some medical procedures such as dermafiller injection or fat transfer would improve the overall appearance of hip dips, but again result varies according to individual and they may not be completely go away. 
Do arrange for a face to face consultation with a certified doctor, it would be a good start. Cheers and hope it helps.