Reloading -
Sounds like you’re just starting out with LR/Precision shooting. If you’re asking about dies and components, then I assume you have a good press, scale, powder throw, calipers, caliber specific comparators, case trimmer, lube, bullet puller, etc...... if that is indeed the case then I would buy dies and components. The spotter and kestrel would go to the bottom of the list as you should be able to do fine on shooting steel through the 20x + power optic most people shoot long range with. If you have a private range then you don’t really need a chrono “yet” either, though that purchase would come immediately after load components to make things easier on your load data.
Magneto-
You can measure off an assumed velocity and then tweak the MV in ballistic AE and figure out what your MV is, based off of where your rounds impact vs the water line. It’s time intensive but it works. If your barrel is cherry expect your MV to change after 80-150 Rounds and speed up a bit. It’s hard to figure SD and ES without a chrono, especially if you’re shooting 500 and in. A 60 ES May not show at that distance but I assure you it will beyond that. Again, that’s where a good chrono comes in.
Kestrel-
I have a kestrel but I don’t use it unless I’m shooting past 1200. I just hit the update weather function on my AE app and it gives me an accurate enough solution for 1-2 MOA targets, if I miss it’s my fault not my dope.
Spotter-
I do love my S2 82 20-70 Meopta but that was a luxury purchase after 80-100K in gun stuff. I love phone scoping my load data so I can do latter tests and dope verification at just about any distance. Don’t get me wrong I can see a 2” dot at 800 with a 24x scope but watching trace in video is nice....just not necessarily necessary ha.
Mags, bags, and other gear-
Look for sales and check the PX. It’s amazing how fast you start to accumulate supporting gear, save some coin and buy quality used kit.
Good luck, especially if you’re married! Ha