Didn't the shop suggest you for what are te "necessary" accesories ? Well it's okay, let me suggest.
(1) UV Filter to protect your lens.
I suggest. . . B+W UV Haze F-Pro, Hoya HD Pro 1 Digital
(2) Lens Pen to clean off finger prints on lens
I suggest . . . The $12 one from TK foto technic
(3) Blower to blow off dust
I suggest . . . The $16 AxF brand from TK foto technic
(3) Tripod for night long exposure
I suggest Sirui T-1005 with G-10 Ball Head $180 from TK foto technic
(4) Camera Bag
I suggest
For sling, get Crumpler 5 million or 6 million from TK foto technic at $100 and $140 respectively.
For backpack, get Lowepro Flipside300, Fastpack200. $100+ from TK foto technic