Now for some suggestions. I kept it separate since everyone has their "best" radio.
First off, unless cost is no object, ignore the fancy stuff like digital, APRS, etc. That will really jump your cost and add to the learning curve. If your used radio has it, fine, but don't worry about it just yet if you have to pay for it. Also note that a dual band radio is often a fair bit more than the same brand's single band version so it's good to think about if you really need both bands. Personally, I find it good to have both, but if most of the repeaters in your area are only on one of the bands you may be able to save several bucks.
Second, try to stay with the "big three" brands, Icom, Kenwood, and Yaesu. You'll end up with a quality radio and most clubs (or even repeater groups) will know and understand them and be able to quickly and easily help you out with issues. You'll generally pay a bit more but will probably find it will be worth it. Be aware though that each brand has it's own way of laying out the radio, especially the menus. You may not need to access them much once you program your radio, but there'll always be a time when you need to make that one change in the field with no manual around. Further down is one solution to this.
Avoid a commercial radio as your first radio. Sure Motorola, Kenwood (professional series), and others make great radios that work well, take abuse pretty well, and many folks say are the only ones you should ever use. There are some real down sides though. They're designed for untrained users that only know two things, push the mic button to talk and release to listen, and select between the few programmed channels only when you must (and always return to dispatch when you're done). They're hard to program (folks often will be happy to help with this though) and you can't use it for anything but exactly what's programmed (I'm ignoring FPP - Front Panel Programming here since it's rare or a hacked option in many cases). If you need to make a change (even for temporary use) you'll need to break out the programming software, interface, and cable and make your change (and hope you don't mess anything up in the process). They also have fairly few channels you can program and scanning is slow and often doesn't work as expected.
There are some low-end radios that may work. Often they are lower power and have the same limitation of only what's programmed can be used. Basically they're the mobile version of those cheap Chinese handhelds folks have already warned you to avoid. Unlike the handhelds though, they're priced much closer to the "big three" prices for their starter radio line.
There are some options for programming your radio using a computer. Note that when I say a computer, this generally means a Windows based computer. No Mac, No Linux, no Netbook, a real Windows computer (generally Windows 10, but often 8 or even 7 will work fine, the further back you go the less luck you may have). Chirp is one example and it handles many different types of radios, but may not have each and every feature or menu item programmable using the software. Some of the "big three" offer free programming software as well they generally are model specific but will allow you to program every option (but many call them difficult to use). You can purchase software that's designed specifically for a single model of radio from RT Systems that's good software but if you change models you'll need to buy new software. For the commercial radios, you'll need to purchase their expensive software, their expensive interface box, and their expensive cable. Many of these are specific to one type of radio so you may end up needing to get several expensive things to get your mobile and handheld to work like you want. Be aware that if you get old commercial radios, you may also need to find an old (perhaps very old - think 1980s models running straight MS-DOS) and the software, interface, and cable may no longer be available. Some have found it online and a few even got versions that were virus free! Like I said earlier though, some hams do have the needed hardware and software to program them and many are happy to do so at no charge for hams that agree to their standard loads or (if you ask really nicely) have a well organized and fairly short list of everything that needs to be programmed.
I hope this helps!