For me the essentials are:
good quality scissors
lots of pins
pin cushion (makes life so much easier)
tailors chalk (don't buy the pencils - they suck)
Plenty of different thread colours.
needles - different sizes.
I also find it really useful having lots of bobbins - i went and bought a whole bunch and made a bobbin with every thread i had and store them in a little bobbin container. So easy being able to see them all clearly and grab the colour you need. Before this i only had about three bobbins and was winding new colours on every time i had a new project - annoying.
I think most other stuff you can get as you go - wait until you need it and grow your collection that way.