You need:
Studio monitors
MIDI controller
Soundcard
Microphone (optional but handy)
Decent set of closed back headphones (optional but advisable)
STUDIO MONITORS
- very much a get what you pay for situtation
- good brands KRK (rokit series are considered best budget monitors), Adam (very good brand, higher end products and price tags), Dynaudio (very high end products), Yamaha (good very versatile range that's strong throughout).
- be sure to look at correct positioning of monitors to get the best out of them
MIDI CONTROLLER
- depending on your uses a cheap one may be more than adequate.
- Alesis Q49 (I use this) is a solid reliable controller with octave shift, pitchbend and modulation wheel.
- If you need more controls i.e. knobs and faders that you can use for altering automation etc. in logic then I recommend M-Audio Axiom 49.
SOUNDCARD
- if you are producing electronic music then you may not need this, but it is good you you can run the audio drivers on it
- also gives you the option of recording something if required, im sure recording vocals at some point will come in handy
- focusrite saffire 6 USB, 2 awesome pre-amps, very good build quality, I have this and can't fault it. the only reason I would ever change my soundcard is if I needed more pre-amps, and I would stick with focusrite, can't recommend the company enough.
MICROPHONE
- if you do need to record vocals for a track then you will need a condenser microphone, this is always best to have in any studio.
- go for something simple if you aren't going to do do much recording
- Shure SM58, or (its a bit more expensive but a lovely versatile mic) sE Z3300a
HEADPHONES
- not essential but prefect for when producing late at night
- it is also beneficial to listen to your mixes on headphones as well as monitors
- Audio Technica ATH-M50, KRK headphones, most closed back headphones £80 and up should do a good job, wouldnt worry about focusing too much money on them.
- i beg of you DONT BUY BEATS BY DRE, they are worse than useless in a studio set-up
I hope this has helped you, if you need any more advice feel free to send me an email.
Also, my website is themusictechsite.wordpress.com (it's still under construction) it will hopefully help you out with gear and production. I advise you to follow it as well but as it's not finished new sections are being added and updated all the time and following it will notify you of the sections coming online.
Footnote: This equipment will not enhance you're musical talent, it will only better communicate your talent into a song and make it easier for you.