Karlie here from the Shopify Support Team! It sounds like you may be looking for either an app that would allow you to offer your customers a group of products instead of just 1 product, like a bundling app or possibly a tiered pricing app that would allow you to set up prices depending on how many products a customer adds to cart. I'm happy to list a few options below so that you can look into the apps to see which one would work for you.
Bundling apps: these apps would provide your storefront with a feature that allows customers to bundle together products to offer a combination of different products priced as one. Some apps will allow you to set custom prices for these bundles as well. If you're interested, you can check out all of the bundling app options here.
Specifically, I would recommend checking out:
Quantity Breaks and Tiered Pricing apps: these apps allow your customers to select multiple products in your store and have those products discounted depending on the rules you have set up in the app. You can check out all of the apps that offer quantity breaks and tiered pricing, here, but specifically I would recommend checking out:
If these options don't quite work for your business idea, then you could always look into hiring a developer or a Shopify Expert to customize your store to your liking. Shopify Experts are developers, designers, marketers and photographers who you can hire to help you with different aspects of your online store. You can check out our Shopify Experts, here.
I hope this has answered your question. If not, or if you have any further questions please let me know. I will be happy to help!