Everyone is different, but the standard one year of Med/Surg is still solid advice. You need to get your skills down before you start taking on the harder stuff, where things are being thrown at you in rapid succession.

However, if you feel like you've learned a great deal already in the ER, then there is nothing that says you can't start in the ICU or ER. But you will need to look for a good teaching hospital that has special programs for new grads who want to start their careers in those areas. Where I live, the local University Hospital offers one year internships for new grads in both the ICU and the ER. So start investigating some of these places now, and see if this is something you think you would like to try.