Welcome to the fun! Following on from Bernardsmiths excellent advice, here are some things that I have tried in order to "improve" store bought juice. I have also been doing some Covid experiments.
I usually press my own apples (I am on a couple of acres with eight apple trees which are mostly eating types but there are a couple of "mystery pippins" and a crab apple... together they make quite a good cider). However with the drought and bushfires here in our region of Oz this year the trees didn't produce any usable fruit, so I had to try store bought juice.
Firstly I tried "Graham's English Cider" using preservative free store bought juice. There is a post for this somewhere on the Forum and it uses black tea and limes as additives (roughly, the recipe is four black teabags and three key limes or one ordinary lime to five gallons of juice). It was a bit rough to start and took about six months to mature into a pleasant, easy to drink quaffer. I have found that store bought "drinking" juice by itself loses flavour as the yeast consumes the sugars. Although I understand that fans of "turbo" cider don't find this to be an issue.
The second effort involved blending two different single variety juices (Granny Smith and Pink Lady). The tartness of the Granny Smith blended well with the "off sweet" Pink Lady and using SO4 yeast, produced quite a good cider.
I also "dry hopped" some of these. This does wonders for any "ordinary" cider and involves putting 3g/litre (about half an ounce or less per gallon) of dried hops in a tea bag and steeping it in your secondary ferment. A word of caution with doing this... hops float, so you have to weigh the teabag with marbles or something similar.
I dry hop at the very end of secondary fermentation, just before bottling and only for a few days. The trick here is to taste, taste, taste, because the cider takes on the hop flavour quite quickly.
Enjoy the ride!