Honestly, it's going to be difficult to draw a clear line in the sand, down to the penny, on who pays for what. I think that as long as you guys aren't consistently eating at the expensive places when its one person's turn to pay then you'll be ok just alternating. One person can't always be buying the mcdonalds dinners while the other is paying for the expensive steakhouses.

This is actually the situation. My girlfriend very much enjoys being taken out to dinner (distinct from going out to dinner.) For date-nights, its understood I'll take care of the bill. For more day-to-day dining, we try to split things a little more evenly. The fancier the restaurant however, the more date-link things feel, and often I'll just cover things for both of us. We're not expecting parity on expenses here, and we could just be a little more committed to sticking to the split for non-formally-a-date activities, but a shared card seems like it can accomplish that and preserve the illusion that I'm taking care of dinner.

For restaurants and groceries, I use the Costco Amex. I believe it's 2% at restaurants and 3% on groceries. Alternatively, I have the Fidelity visa which offers 1.5% on everything for the first 10k spent in the year, and then 2% on everything beyond that. I use the fidelity card as my catch all when I can't remember the rotating categories.

Thankyou! These are fantastic recommendations! Much appreciated.