That may not be working how you think. Its integrated with the card, unlike system memory which you can replace individually up to the supported limit. The amount of VRAM available depends on the card and once you get it, that’s it.
As others noted, getting something “big” is going to cost a lot of money for something that’s going to be virtually idle most of the time. If this is just hobby work, then you’re probably looking at a card in the 6 - 8 GB range for cost effectiveness. If you’re still coming up short with that (after optimizing) then it’s time to start looking at online render farms for the final pass, and simplified settings for checking. If this is professional, you’ll need to check your budget to see if you can recover the additional costs of the higher priced cards.
Regardless of whether or not a scene will work on your card it’s still good to get into the habit of optimizing. Maybe not to the nth degree (diminishing returns and all that) but keeping things efficient will reduce problems.