Conditional items for ordering

I'm trying to build a store where you choose your items to combine.

For example: Build your own card - $10

• Step 1 - choose your card (there are 8 choices) 
• Step 2 - (required) choose your art (there are 100s of choices) - after art is chosen, you add to cart.

There is also a page where you can buy the art by itself (which is $8) so I'd want that art page to be a copy of step 2's options. 

Thanks for your help. Hope this makes sense.