I have a large prairie type border, whitewave. Not sure of the actual % of grass to flowers but there's definitely more flowers.
Piet Oudolf has created some stunning praire gardens and his books and YouTube vids are well worth a look for inspiration.
I have planted Eupatorium, Calamagrostis, Helenium, Echinacea, lots of Achilleas, Miscanthus and Deschampsia.
I'm always adding to it because space is not an issue. I can recommend Eupatorium because it doesn't need staking, spreads quickly and props up other plants.
Smaller ornamental grasses can go at the front.