I would vote for a 22 caliber rifle in the action of your choice.
A bolt action, lever action or single shot requires a bit less maintenance than an automatic would be easier and safer for a novice (spouse or child) to use.
Most bolts, levers and single shots are capable of functioning with 22 shorts, 22 longs, 22 CBs, 22 long rifles and 22 caliber shotshell ammunition. Automatics are generally limited to one cartridge length, most commonly 22 long rifle.
A 22 caliber rifle is inexpensive to learn to use not to mention great fun.
Ammunition is common. In this area you can usually find it in most convenience stores, gas stations, groceries and maybe a box or two in most pickups.
You can purchase a large amount of 22 ammunition economically.
It is easy to carry and store a large amount of ammunition.
And for versatility, you can feed, defend or entertain yourself!
If you opt for a shotgun or a centerfire caliber rifle, purchase ear plugs or muffs. When you learn to use it, use the hearing protection and wear glasses ( sun, shooting or prescription ). The ear and eye protection with help with what most people consider 'recoil'. If you need to use a gun in the field, you don't notice the noise or muzzle blast but shooting recreationally will bother the ears as well as the pocketbook on large caliber or gauges.
I'd also recommend ear protection for shooting a rimfire rifle. It will allow you to concentrate on shooting accurately without anticipating the noise each time you pull the trigger.
Another add on to purchase regardless of what you choose, would be a universal cleaning kit. It should include a cleaning rod, oil, patches and a bore brush. The universal kit will work on pistols, rifles (including rimfire) and shotguns. In most cases all you need to add is whatever caliber or gauge bore brushes you need.
Good luck with whatever you choose. You are going about it correctly by doing the research and as someone said in an earlier post, shoot different guns if you have an opportunity and that will help you make an educated choice.