In order to have a great jawline like Ariana Grande, what do I need to get?

A chin implant could improve the shape and projection of your chin. When well placed by an expert, a chin implant can last for decades or a lifetime. You can choose a chin with will give you a better projection and smooth the jawline. A consultation with a board-certified facial plastic surgeon is important; for the patient to be evaluated, their goals discussed, and a custom treatment plan decided upon. I hope this helps.

A well defined jawline, in either men or women, requires a total augmentation of the entire jawline. This can be done using either standard chin and jaw angle implants or a one-piece custom jawline implant based on the patient's natural jawline shape. Often soft tissue reduction procedures have to be done around to maximize the result.

 The photographs are not very helpful, however it does appear that there's a weak and recessive chin profile for which a chin implant can improve significantly. Chin implants are manufactured in a large assortment of both sizes and shapes, and are usually placed under local anesthesia as an outpatient procedure. For many examples, please see the link and the video below

 Hi, I have performed many facial shaping procedures, including Chin Augmentation with dermal fillers or silastic chin implants, for over 30 years.  From the photos, your chin is very weak.  When the chin is weak, this creates an imbalance making the nose appear larger, the mid face top heavy, the lower face looks short, de-emphasizes the lips and allows early formation of a "double chin".  
 Proper placement of a silastic chin implant adds forward projection to the chin thereby creating harmony and balance to the lower face.  Using the same incision, liposuction can be performed to reduce the fat and further shape the neck.  Excess skin, from below the chin, can also be removed through the same incision.  
 I have found that placement of a silastic chin implant, through a small curved incision under the chin (also allows excess skin removal) to be very safe, quick, highly effective and far less invasive than a sliding genioplasty (requires extensive tissue dissection, bone cuts and placement of metal screws and plates to secure the cut segments of bone).  I perform chin implant surgery in 30 minutes or less, often using a local anesthetic alone.  In my opinion, you are a good candidate for chin implant surgery.  
Hope this helps.