Well this is a very wide open thread that could go a million different directions.
As a gun nut, I will say this; a firearm is a tool. Think of it as a hammer. There are a bunch of different types of hammers for multiple jobs. You can bang on everything with 1 hammer, but it doesn't mean that hammer was meant to do that job.
firearms are much the same way.
First determine the JOB
Second determine the Tool (rifle & style of rifle, shotgun, pistol, revolver, semi-auto etc.)
Third (and by this point the second choice will have narrowed the feild considerably) Pic your Caliber or shotgun gauge.

I do not like the idea of a 1 gun for everything, but you can get away with any 3 of these 4.
one hand gun
one shotgun
one rimfire
one centerfire

But even doing that you have to buy one first, right. So wich tool is the most important to have first. Only you can answer that.

I have a decent collection, but setting here thinking, if I owned no guns at all (wich means I am not an avid hunter), what would I get first. For me it would be an AR15, m4 congfiuration (16" barrel)

They have very little recoil wich is good for a new shooter (unlike a 12ga, 30-06, 44mag, even 45auto) The report is rather loud, if that is a concern though.

Home protection is covered.

Survival is covered (large and small game) & No a .223 will not vaporize a squirrel or rabbit, just shoot it in the head, hence removing the head. Deer and hogs are shot all the time with .223's firearm regs be dammed.
JMO

Something along these lines: