How do you figure out what school supplies you’ll need for the year? I know you need pencils, crayons, glue sticks, etc, but what about special supplies? How do you figure out what art supplies or random things you might need?
I’m planning my first year and am curious.
Following because I’m in the same boat. 
What age(s) are you teaching?
So far I’ve purchased butcher paper, crayons, markers, colored pencils, pencils, erasers, tempura paint… I think that’s it.
What curriculum are you using?
I have 4 1/2, 7 and 9. We’re using Abeka Math, Learning Language Arts through LIterature, God’s Design for Life (science), and Mystery of History for basics. I plan on using COAH’s Preschool LOW program for the youngest.
My mom has homeschooled up until now. It’s going to turn into an adventure for all of us!
Cool. Good luck to you! Mine are 7, 5, 3 and 1. We’re starting with Bookshark.
Typically the curriculum will list any supplies you need, either somewhere in the notes or within the lessons. I review that and note anything we don’t typically keep. Other than that it is just replacing anything that needs replacing.
For LOTW she has a suggested supply list in the download. I think most of it was books we could get at the library and stuff we had laying around the house (crayons, pencils, etc) except a laminator (which I am not using) and do a dot markers (which you can get the Crayola Stampers markers at target a lot cheaper.
Dollar tree has individual colors of bingo dotters for a $1. They don’t say non-toxic and they don’t say washable but they’ve been fun for my older kids (11, 8, 7) to play with. I think there’s only 5 or 6 colors. Just another cheaper option for the do a dot markers if you’re comfortable with your kids playing with them.
As far as supplies, we replenish all of the basics and then I look at each curriculum and determine what I’ll need. For example, the writing curriculum my daughter uses required a binder, divider tabs, lined paper, and a comprehensive thesaurus. The art curriculum I use with my younger two has a supply list already in it so I just bought what we didn’t already own.
I also buy any supplies that I will need to replenish throughout the year…toner, colored copy paper and card stock, page protectors, etc. I used to buy laminating film a lot when my kids were younger and I laminated more, but I don’t need it as often now.
Another thing you can do is figure out how you will organize all of this and then buy the supplies to make it happen. For example, when I bought the bingo dotters, I went ahead and purchased a plastic container with a lid to put them in along with the art paper they’d be using the dotters with.
I try to buy as much as possible in the summer so I don’t have to think about it during the year. Not to mention, there are usually some great sales/deals going on. Paper, notebooks, pencils, folders of course - those are all mega cheap this time of year. I don’t go overboard buying these, but if I have leftover then it’s that many fewer I have to get next year. We are craft/project/experiment intensive in this house, so my main purchases revolve around craft supplies… playdough, model magic, glue sticks, glue bottles, bingo ink blotters, paper of all sorts, colors, sizes, glitter, craft sticks, different types of paint, etc… basically anything I think/know we will use. I’m the type of person that if we don’t have the stuff on hand in the house, the project usually won’t happen because I’ll push it aside until “later”. By grabbing what I can now we have a good chance of getting things done (and remember the sales!) Happy shopping! 
I think there are must-have supplies that we all use, but also supplies needed depending if you are planning a lot of crafts, have older children, etc. Check out my free supply list here that helps you decide what supplies you are going to need based on your family.