Every year, teachers provide a list of materials needed for their classroom for the school year. If you've never created a list before, this list may be helpful to you. You can use it by itself, or as a starting point for your own classroom list. I've included all the student and basic classroom supplies you will need throughout the year and where to get them.
When I taught 4th grade, my school had each student in my classroom pay a $25 student supply fee. We used our school's credit card to make our purchases, and then turned in the supply fee money that our students gave us during the first week of school to cover our purchases. My 4th grade teaching partner and I went to the store a few weeks before school started and gathered everything on the attached Student Supply List. We were then able to put all of the supplies together and put them into the student's desks so that they were all ready when parents and students came to our Open House Night before school started. We were also able to organize and store all of the leftover materials in our cabinets. Purchasing supplies this way made sure that EVERY student had the exact same materials, and that they all had ENOUGH materials. This way there weren't any students with "cooler" supplies than the other students.
We did have a couple of students who couldn't afford the $25 supply fee, however, our school had money set aside for situations like this. You might ask your school counselor or main office if there is money set aside to help out children in need. If your school doesn't have money set aside for this type of situation, you might consider upping the supply fee to $30, to cover students who won't have the money to pay. OR you also could do some sort of donation or fundraiser to cover the supply fees not paid.
Also, it is a CERTAINTY that you will have students move in and out of your classroom throughout the year. I suggest purchasing at least 5 extra sets of everything so you are ready for new students at a moment's notice.
When we went to the store to purchase supplies, we went about 2 weeks before school started. It was my first year teaching in a classroom, and her first year teaching 4th grade. We were both a little overwhelmed with everything we had to do in order to get our lessons and classroom ready, so we didn't make getting supplies a priority. BIG MISTAKE. We ended up not being able to purchase everything on our list. We had to make substitutions like buying spiral notebooks instead of composition notebooks, purchasing crappy pink erasers instead of the awesome Mars erasers, etc.
My tip is to make purchasing supplies a priority! I suggest going to the store 4 weeks before school starts if possible. This way you should be able to get everything on your list with no problems, and you will avoid the rush of others preparing for school. Your trip should take a couple of hours.
P.S. If you have a friend or loved one that can go with you to do this, that will be a HUGE HELP. I had to push/pull TWO carts by myself because I had so much stuff!