When I was a kid, store-bought walkie talkies transmitted and received on CB channel 14. More recently they were FRS (Family Radio System) frequencies. They're garbage you can buy in blister packs at Walmart. They're mostly .5 watt and are limited to 2 watts by law. GMRS (General Mobile Radio System) are newer and becoming popular and are allowed up to 5 watts on some channels and 50 watts on the higher channels. GMRS is better than CB in that power allowance and the fact that every braying jackass on the planet can and does use CB. GMRS requires a family license which will be going down to $35. Universal Licensing System
These are what I started with. They're good radios and can do line of sight up to five or six miles in reality with fixed antennas. That's where the curvature of the Earth stops almost all UHF signals without elevation.
I used the Wouxun KG805 walkie for a base station and it worked pretty welleven though it's only five watts. I added the below with a base station and can reach out pretty far. This is a 40 watt radio.
The 905G is similar to the 805G but is IP66 rated which makes it much more weather resistant. Wouxan is rumored to be working on two next generation variants which will be IP67 rated.
This antenna makes them even better. I have one of them to use on trails. It's 6db gain. MicroMobile® MXTA26 6db Gain Whip Antenna | Midland Radio.
There is a lot of information on GMRS on Youtube.
There is a lot of equipment out there which is utterly unsuitable for defense or even range use. Here are some recommended companies you can trust:
Muddy River and Bravo are lower cost options. They won't likely last as long as the higher cost equipment, but they are safe to use and check all of the boxes.
In 9mm, .40, and .45, it's easy. Find Speer Gold Dot or Federal HST in any bullet weight, +P or not. In .38 Special and .380, especially out of a short barrel, there are no really outstanding choices. I recommend .38 135 grain Gold Dot and .380 Hornady XTP.
One of the best ways to learn about self-defense and shooting is through good old-fashioned book learnin'. Here are a few I recommend: