Ahh! There's nothing like the smell of new crayons to get you going in the morning! I love scent of brand new school supplies!
In my first year of teaching Kindergarten I was totally clueless about what supplies I would need as a teacher and what supplies my students really needed. The first thing to keep in mind is that it takes years to build a perfect classroom, don't expect to have all the supplies your fellow teachers have. Here are a few examples of some items that you might want to consider splurging on your first year.
For the teacher:
A good stapler, a three hole puncher (I got a great hole punch and pencil sharpener at Sam's), lots of pens in a multitude of colors, a lanyard for your classroom keys and whistle, a clip board, varying sizes of binders, manila folders, ziploc bags in varying sizes, permanent markers, invisible tape, masking tape, electrical tape (this works great for marking where students are to stand when it's time to line up), and very very comfortable shoes! Take it from me...don't wear brand new shoes your first day, you'll be so sorry!!
For the students:
Individual sized dry erase boards (I know these can be pricey, but you'll get a lot of use out of them), a package of men's tube socks (these are used as erasers for your dry erase boards and they hold the marker!)
lots of baskets and containers (they have a great selection at the dollar store), playdough, beanbags (try orientaltrading.com), books (goodwill is a great resource as well as garage sales), a pencil sharpener, extra crayons, markers, dry erase markers, printable labels, clip boards, and pick out a cute theme for your classroom. If you're teaching Kinder specifically, you'll need a calendar, days of the week, months of the year, colors, numbers, and words for your word wall. Luckily many teaching supply stores sell these in a set and they have some really cute themes! Check out www.lakeshorelearning they have lots of awesome sets. Be sure to laminate everything before you put it up so you can protect your investment.
Lastly be sure to keep your receipt! In Texas you can write up to $300 off of your income taxes for work expenses. Some schools will reimburse you for some purchases so make sure to ask a fellow teacher. Although I've never had this happen to me, but hey you may get lucky!