All-purpose in terms of multiple positions on the baseball field or all-purpose in terms of baseball and softball use? If it will just be used for baseball and you want a nice glove that you would like to have (and cherish!) for years to come, get a Wilson (make sure it's leather). Anything from 11 to 12 inches should serve you well for a glove that can be used at about any position. If you plan on using it in softball you could extend your range from 11 to 13 inches.
Rawlings is the other brand to consider. Mizuno and Easton are usually good, too. Nokonas are too expensive and overrated, in my opinion.
Again: Leather, 11 to 12 inches (could use in infield or outfield), Wilson or Rawlings.
Make sure you keep a baseball where the pocket and palm meet. Stretching a rubber band around the outside of the glove (around where the baseball is) will help you form a nice structure to your new glove.