How to start afresh at 26?

This should be a group of people 26-30 Age group who wish to do it all over again right from their graduation and in a way have a plan to do it now!

Say You did engineering say mechanical, say u worked for 2.5 plus years in IT Job. Say u dropped to prepare for CAT etc after that, say 4 tyrs post graduation and with 30 odd months of IT experience and average CAT score to show for, how does someone start planning o become an Investment banker with or without MBA?