Looking for a good bang for your buck? Consider the 90’s Sega games like Godzilla, Goldeneye, or X-Files. Gotlieb also made some DMD games that are neat like Gladiators.
Keep in mind though that if you get an older game that is more shallow than the Sterns of today you’ll want to set it up to be challenging with open outlanes, harder to start multiballs, and short ball saves or you’ll get tired of the game in a single game collection. The Sega machines are heavy on the multiballs and are generally easy to commence unless the settings are changed.