I started losing mine at 17 and took the lot off straight away. I now do a grade 0 every couple of weeks. There’s no point prolonging the balding process, once it’s going it’s going so get rid of it.
Don’t skimp on clippers, buy a decent set straight away as not only are you saving on the barbers, but you’ll save on clippers in the long run. Ceramic or self-sharpening steel are the ones to get, built-in battery so you can charge and then use wireless. I got a nice £50 pair of phillips ones on offer at £35 about 5 years ago and they’re still going strong.
Other top tips: get a small hand mirror to check the back of your head in the main mirror. Failing this, take selfies of the back of your head on your phone (a handy skill to acquire), but remember to turn wifi off if you have auto-upload, or expect 50 odd photos of the back of your head to accumulate on there.
Final tip: Sun cream.
EDIT: Always thought the circular type clippers sc-xc linked to were a bit of a gimmick, but could be worth a go if they’re that good.