As someone has said, this is an addictive hobby. I make ciders, fruit wines (I just racked a pineapple wine to secondary on Friday), and meads. All of my suggestions (except for echoing someone's comment about priming sugars and bottling--I'd listen to them) are optional, totally over and above what you absolutely need, but may help. Some of these things are especially helpful if you're doing a bunch of gallons.

I bottled a Kirkland apple cider last week, and a couple of gallons of grocery store-purchased Louisville Apple Cider two weeks before that. I haven't had either yet, so I don't know how they are; however, they tasted great at bottling. I did two gallons of the Louisville and a gallon of Kirkland--I didn't add water, only the jug of juice. (There was a Suja(?) organic spiced apple cider in a red bottle in the refrigerated section at Costco around Nov/Dec, which tasted really good, but it resulted in a watery cider). Make sure the ingredients list on the juice doesn't contain anything that has * something * sulfites as those are used to kill the bugs, and it will hurt your yeast. Citric acid/ascorbic acid is vitamin C and I'm realizing is put in everything. Some people use the frozen apple juice concentrate--just remember to add non-chlorinated water (bottled spring water is best).

You can get four demijohns on Amazon for $40 ( https://www.amazon.com/gp/aw/d/B084KZ33FJ?psc=1&ref=ppx_pop_mob_b_asin_title ). You should just buy the four now and save yourself the hassle of ordering more later. 😂 I tend to go for the three-piece bubbler, but the one piece is better for aging in a bottle (which you don't do for cider, but meads and wines have a long secondary fermentation time).

Enough background stuff. What you have listed (plus bottling stuff) should get you a perfectly fine cider. But here is the part you asked about. Additional things I used, and they really are optional:

Notebook. Or a Word document. Write things down so you can repeat (or avoid!) later. Which spices and how much did you use? Which yeast? When did it visibly start bubbling? When did it visibly stop? What brand of apple juice? What date did you start the batch? What was the OG? What was the gravity reading on day x so you can tell it's done fermenting? FG? Did you use kieselsol and chitosan to clarify? Which day? When did you bottle it? How much priming sugar? How did it taste when you bottled it? After it aged for a month? Was it bubbly enough?

Spices. I added half a tsp of whole cloves and a cinnamon stick to the fermenter. I wanted an apple pie flavoring.

Sugar. Not necessary at all--I didn't use sugar in mine. But if you want a higher abv then you may need to simmer sugar and water to make a simple syrup to add to your must (is it called a must for ciders? It's what you're going to add yeast to in order to make something ferment). How much? Google it. Take into account your yeast tolerance (it should have an abv tolerance you can find with a Google search). Yeast will eat up sugar to its tolerance, allegedly (sometimes more, sometimes less).

Paper Towels. Because I'm always spilling. I put some down for when I bottle and rack because that little hose sometimes gets away from me.

Acid blend. I added a tsp of acid blend. It's a mix of three acids in powder form (citric acid and two others), which change the taste a little. Completely optional, but make it taste...better. I know I added a tsp of acid blend because I wrote it in my notebook.

Food scale. Also completely optional. I got one at Costco a couple months ago for $20--it does pounds/ounces and grams. It's good for measuring some things (like priming sugar!). I make a lot of meads and wines, so I use it for measuring honey and fruit.

Pectic enzyme. I don't know if this is even necessary for the Kirkland apple juice because it's so clear that it looks like it's already filtered. If you're using a murky cider or fresh fruit, pectic enzyme pulls the fruit gunk to the bottom during/after fermentation. The role is to make your cider clear, and, because the Kirkland juice is clear to begin with, but I used it anyway. I added 1 tsp pectic enzyme per gallon at the initial mixing (it says so in my notebook). If you were using fresh fruit, it's a definite thing--add it at the beginning. There are other enzymes for different things.

Yeast nutrients. I make mostly meads, which need a little extra nutrition to ferment all the way; I doubt you need it for apple cider, but it's habit for me to put it in. It helps when your final abv is over 10%. (The Kirkland juice for me was OG 1.052, FG 1.006, which is a little high--I should have taken gravity readings before bottling to be 100% it was done. The final abv for mine should be around 6%.) My notebook says I added 1 tsp.

Funnel. You probably already have one. It helps when pouring things into the demijohn, and if you pour things into a bottle. Note the size of the hole as you may need two sizes. Remember to sanitize it.

Bucket. Actually, two buckets. One big enough for mixing sanitizer and dunking things in to sanitize. I have a 2-gal with a lid that I keep a batch of sanitizer in for a couple of weeks at a time because I'm always starting/racking/bottling something. A second bucket (or use your first bucket of you're not keeping sanitizer) big enough to put your demijohn in (I have a 7-gal for this) in case it bubbles over--it makes cleanup a lot easier. Optional because you can use containers you have around the house.

Kieselsol and Chitosan. If this is your first batch, don't bother. I use these to clear because I'm impatient. This practice for me is a carryover of mead and winemaking. You add kieselsol on one day, the other a few hours later (I usually do the next day), and bottle the day after that. I think that's the order--I have to look up the order every time because I forget. One is positively charged, the other is negatively charged, so they attract stuff floating in your cider and sink it into the lees (the gunk on the bottom). There are other things that clear your cider, including time.

Bottles. There was a great suggestion about bottles, caps, and a capper. You can get swing top bottles and not deal with caps and capping, but the swing top bottles are expensive. Do you want 12oz? Pint? Liter? If you're making sparkling cider, you can't use corks because the pressure will push out the corks and you'll have a mess! If you're doing a gallon batch, how many 12oz bottles will you need? How many pints are in a gallon? How many liters are in a gallon?

Bottle Rinser. One of the best things I bought was a pump action for squirting sanitizer into the demijohns and bottles. I love it, especially when I'm bottling two or three gallons of something because I have to sanitize 8,934,721 bottles. Again, not necessary, but I wish I'd bought it earlier. (And with this link, you know where I live!) https://www.austinhomebrew.com/Monster-Cleaner-Bottle-Fermenter-Rinser_p_10130.html

Bottle Drying Rack. Not necessary because "don't fear the (StarSan) foam!" When you rinse bottles, you stick them in the rack upside down for excess cleaner to run out. I put newly rinsed bottles in it to dry before I store them.

Priming Sugar/Corn Sugar/Dextrose, as someone mentioned. If you don't do this, your cider will be flat; if you do this, your cider will be bubbly. You do this step when you bottle. You can use any fermentable sugar for carbonation. Google "cider priming in bottles" to help with process and calculations so you don't have bottle bombs. (Note: you can mix sugar with water and simmer for a few minutes and then add to a sanitized bucket and rack your cider onto the priming sugar solution to mix with your cider and then fill bottles from this bucket, or you can add the priming sugar in powdered form directly to the individual bottles--but which way is easier? Definitely the bucket method because you're not trying to put an eighth of a teaspoon or whatever into each bottle, but you lose more cider because you're racking twice).

Non-fermentable Sugar. If you want your cider to be a little sweet, you add this. How much? It depends. Which sugar? It depends. They have funny spellings: one begins with an x, one is stevia, which might have a funky aftertaste; I just ordered some maltodextrin that I'm going to experiment with later. Google it if you want a sweet-ish cider because the yeast will eat through the sugar in the cider.

Spray Bottle. When I mix a batch of sanitizer, I put some in a spray bottle. I always forget to sanitize something, or some things don't fit into my sanitizing bucket (e.g., the long handle of my stir stick to punch the caps--submerge the floating fruit bits--on my meads and wines). It's a great tip I wish I'd learned earlier.

Bottle Filler. I have never used a clamp, so I don't know how it compares to this. Used for bottling, it's a rod that's spring loaded with a shut off. When you put the rod on the bottom of the bottle, it opens the valve and fills your bottle; when you lift it up, the valve closes and your cider stops flowing. It helps get consist amounts per bottle, and makes things a little less messy when you move your tube from one bottle to the next. It's often sold with an autosiphon. https://www.austinhomebrew.com/Bottle-Filler-38-standard-size_p_641.html

Labels. In three weeks you may not remember what's in the demijohn or bottles. I'm super fancy, so I use painters tape and a sharpie. Because I have a bunch of things brewing at a time, I also label the demijohns, and my bucket of sanitizer. What's in it and the date are the most important things to write down. Usually the label is "Apple Cider #4 1/16/21 (brew start date)" on the demijohn and on the bottles "Costco Bubbly Cider #4 2/1/21 (the bottling date) 6%" so I know the important stuff at a glance.

Good luck! Let us know how it goes!