Your first week will vary by college, but in general you will have some form of induction to the college and possibly be shown around. In lessons, teachers will generally introduce themselves and what they plan on teaching, so the first few days should be nice and relaxed whilst you get into the swing of things again.
For stationary, buy anything you think you will need to work to the best of your ability - pens, ink (if necessary), pencils, rubber, lined paper, ruler, calculator and maybe a printer too (if so, make sure to purchase extra ink cartridges - going to print an urgent piece of work only for your printer to run out is not a fun experience).