Best (affordable) upgrade option for the Nikkor 18-55mm F3.5-5.6 VR kit lens?

I think it's important that you decide whether you want a zoom, or not.  Reason is that zooms are more flexible yes, but at the expense of some compromise.

- for landscapes some wide angle, or wide-ish, could nail it.  There's the old 20mm f2.8 not really cheap but exists 2nd hand.

- for wildlife the 18-200 is nice and fast-focusing - I ownn it - but not that cheap, and the new lens you're thinking of is probably similar to it apart from the extra "reach".  The 70-300 4.5-5.6 VR is a good deal cheaper.  The 70-300 without VR is cheaper still but the lack of VR could be a problem and it is said to be quite soft beyond 200mm.

- of course a super-zoom like the 18-300mm (or the 18-200mm) covers all your needs at once so could end up being cheaper