There is no such thing as a universally "best" recording of anything, because different people have different tastes. Here I share my favorite recordings of my favorite Mozart symphonies, and I explain why I like both the works and the recordings.
I recommend against buying a "cycle" or complete set of Mozart symphonies. These sets are expensive, and my experience is that most people actually like a small number of the symphonies much more than others. I can't guarantee you have the same tastes as me, but I have noticed that many other classical music enthusiasts also share my tastes in these works, so hopefully this will be a good starting point.
In terms of the symphonies, my favorites are #35 through #41, with 41 (Jupiter) being my all-time favorite, and #40 and #35 runners up, but I like #36-39 and do enjoy some of the earlier symphonies as well.