May sound odd but best purchase I've made has been an ongoing one but it was when I started taking care of my teeth.
I went for a reg check up in Oct 2017 and my dentist recommended a Periodontics who literally changed my life by improving smile tenfold.
At one point, I was having dental surgery once a month. From deep cleanings, him slicing open my gums and removing bacteria and finally extractions and dental implants.
I used to avoid smiling because my teeth were okay but never great vs currently I'm smiling ear to ear.
I used to be petrified of the dentist, now I look forward to my visits. I encourage everyone to go to the dentist regularly.