You can basically do everything with the software - all you really need is a microphone, external sound card, and a DAW and you're set to start recording. Obviously there's more stuff you want but that's a start.
You can also buy DAW controllers with allow you to mix and control effects and play midi instruments. Other things you'll want include a midi keyboard and/or controller, monitors (speakers), and a good recording space. You can also connect instruments such as synthesizers into your computer using your external sound card.
However, these are just basic suggestions, it all depends on what you intend to do with your studio.