Do you have a budget in mind? I tend to recommend the Baratza Preciso as an entry level barebones espresso grinder ($299, but discontinued). If you can find one, it's adequate for many home machines, but can be a little frustrating to work with. Sometimes you can find a used Mazzer Mini or Super Jolly for a similar price used, you'll just need to clean them up and possibly change the burrs (an added expense). A Mazzer is not a multipurpose grinder however, so it will more or less need to be dedicated to espresso. I've heard mixed reviews about the Breville grinders, but I do know folks who really love theirs.