If you are recording audio (bass guitar, vocals), then you must have an audio interface to allow the signal to be converted from audio into data for your Mac. I typically advise the Scarlett 2i2 or Echo Audiofire 4 interfaces for people looking for cheap, high quality, low input interfaces. Either one will work well for you.
In terms of a MIDI controller - you only need this is you want to be playing your synth parts and drum parts on a keyboard. If you simply pencil them in the piano roll right now or use the computer keyboard and it works fine for you, then don't waste money on a MIDI controller. However, if you want to play complex piano parts or enjoy the feeling of piano keys, then by all means pick up a good MIDI controller. You can find them easily on sites like Zzounds.com or Musiciansfriend.com. You won't need a separate interface if you buy one that has a USB output.
You will need a pair of headphones for recording through a microphone. This is to stop the microphone from picking up the sounds coming from your speakers.
In terms of a microphone...you'll be hard pressed to find a definitive answer on one "great" microphone, because there isn't really one - especially in the budget (under $300) range. However, there's a great article about some of the best microphones at each price level here:
Best Microphones
You should be able to find the microphone you're looking for at that site. In terms of pitch correction, you'll want to stick with Logic Pro's pitch corrector or buy Antares' Auto Tune Evo, or pick up Melodyne software to work on pitch correction. You don't want it to be automatic, because the software often messes up and you don't want to ruin a good take because of it.
Good luck!