What is the best way to get rid or age spots and freckles/reduce the AND firm up my neck?

You could take the slow route with skincare (vitamin C, retinoids, plenty of sunscreen) but that will only soften pigmentation marks rather than making them vanish.

You could try intense pulsed light (IPL) which will definitely shift the age spots/freckles and which, depending on the make and intensity at which it’s used, may firm your neck a bit.

Or you could take the quickest, surest route and go for serious lasering with something like the Sciton Halo which is more expensive but which will do it all in one go – here’s a video showing the improvements that one session can make.

Then maybe a few rounds of injectable moisturisers, if you have the budget – they help improve skin condition on the neck as well as on the face, and Revive from Belotero claims to improve pigmentation as well as helping skin regeneration.