Over my years I have owned, shot and hunted with literally hundreds of different rifles, shotguns and handguns. In that time I have pretty well figured out what works for me so that if I were to start from scratch I would likely end up with the same guns and chamberings I use today.
I might choose better wood, but most of my guns are nice enough for me now without being so nice I hate to use them. And I know I'm going to use them hard no matter how nice or expensive they might be.
Even though I might "know" where I was going to end up.....I'd probably not do things too differently. I have loved using many, many different guns and chamberings and learned from each and every one.
When I tell you that I prefer a certain gun or chambering, it's NOT because I've never tried anything else. It's because I HAVE tried and used almost every combination you can think of.....and decided what works best for me based on experience, not advertising and second hand advise. Without going through the years of gun trading and use, I'd not have that knowledge. What I learned is that damn near anything will work if the shooter is good enough, but some just work better.....for me.
If anything I'd likely own MORE, not less firearms than I do.....and that's saying a lot since I now have some 200 firearms in the gun room. I'd trade less and keep more if I had it all to do over.
With that said, I'd likely start with the guns I use most today. First would have to be a good .22 rifle. I've used a lot of really nice rimfire rifles, but keep coming back to the Ruger 10/22 with the checkered stock. It's not the most expensive or best looking .22 I own, but it just works.
For centerfire rifles I'd go with the rifle that started it all. My first true big game rifle was a custom FN Mauser in .30-06....and I've never found any I like as well and still shoot it the most of all my guns. A second Mauser...in .338 Magnum....would handle heavier game for me.
I've owned some 40+ Savage 99's over the years and still love that rifle. I would have to have 99's (probably in the EG configuration) in .250-3000, .308 and .358.
I know, the .30-06 (or the trio of Savage 99's) would cover every need I might have in a lifetime, but I don't believe in going with the minimum on anything. I LIKE rifles and prefer to have a gun for every use.
One rifle that would HAVE to be replaced is my Ruger 44 Carbine. One of my earliest rifles, it has always been a favorite. There are many more versatile rifles out there, but I can think of nothing I'd rather have in my hands if fast, close-up shooting is required and a heavy punch is needed. That little carbine feels like a part of my body and I love it.....and likely why I like it's twin, the Ruger 10/22, is also a favorite.
In shotguns, I am a die-hard fan of classic double guns. My main shotguns would be a pair of L.C.Smith doubles in 20 ga. and 12 ga. These would cover almost every shotgun need I'd ever have. However, for hard-core waterfowling, the doubles are just a little too delicate and since the introduction of steel shot not as versatile as a heavy 3" magnum. For this use the Remington 870 is near perfect.
My handguns would start with the most used....a Ruger 5 1/2" barreled Target Model. One of my first handguns, I have tried many others and keep coming back to where I started.
For hunting, my Ruger .44 Flattop would be my choice. The Super Blackhawk is a bit stronger and also a good choice, but just doesn't fit my hand as well as the old Flattop does.
For everyday carry around the house and woods a 4 5/8" SAA in .45 Colt rides my hip like it grew there. Been carrying one so long I feel naked without it. I would probably add a second SAA in .32-20.....just because I like the chambering and it is a bit better for shooting edible small game.
Of course I could never be without a good 1911 in .45ACP for general self/home defense and carry. It also makes a passable hunting weapon as well.....if used carefully.
I know, that's a lot of guns, but I LIKE lots of guns and that battery would make a nice start if I had to start over. Then I could add a couple of hundred more over the years.....again.
