Not sure what a 357 mag rifle gets you. Maybe a short range deer rifle??
For a rifle, I would get a rifle round.
Good first rifle rounds are rounds like 22 lr and 17 hmr.
If you want something for hunting of some level, I like rounds like 223 Rem, 243 Win and 308 Win. My buddy's first rifle was a Savage 10 in 308 Win. So was his second. This is kind of the classic rifle. His first was the std Savage, which might be too light for someone to hit well with in the field.
Yes, weight makes rifles easier to hit with.
My first rifle was a 1917 Enfield Winchester 30'06 sporterized at 12 lbs including Weaver K4 scope. I could hit anything with that at 12 years old!
Let's talk action type's. . .Generally scoped modern bolt actions are the most accurate rifles. Here is a basic one. . .a Savage 10 in 243 Win:
Together with a 10x Super Sniper, it might look like this(rifle in pic not a Savage):
There are even some unique fun ones like the Ruger Scout Rifle which are fun looking too:
I like lever guns too. A pistol caliber carbine might be real fun. Don't underestimate their recoil. They can be snappy with little to no recoil pad.
If I were getting a single shot, I would likely opt for a T/C Encore or Contender due to the wider barrel selection.