I loved the Rock Band and Guitar Hero games and they are all incredibly dirt cheap to get, so I definitely recommend them. They are my favorite rhythm games. Doesn't matter if you suck, they have multiple difficulties and are a good time. I'm sure you can find some unused bundles still around somewhere, in particular the Guitar Hero guitars I found to be the best ones. The Guitar Hero 2 Xplorer and Guitar Hero: Warriors of Rock guitars might be my favorite as I still own both.
Depending on which system you have right now, I'd recommend the 360/PS3 era ones. There aren't any...BAD ones, mostly depends on musical taste, but I'd personally say avoid Band Hero. It's just a small expansion game that's mostly pop songs. More for the karaoke side of things. Other than that, grab everything else and just play them in order. Probably the best way because both series engines change a good bit or add features and its abit tough to go backwards to play the games, though the Rock Bad games stayed relatively the same.
Also skip Guitar Hero Live, the new one for the PS4/Xbone. The new guitar controls are interesting, but that game is mostly awful. Terrible song selection and it just feels disappointing, especially after how fantastic Warriors of Rock was.