We typically have breakfast in, lunch out, then dinner can be either/or.
We are out and touring or hiking most of the day and lunch out is usually cheaper than dinner so we find local places we want to try. By dinner we are tired so we go 'home' and cook or scrounge in the fridge, depending on how tired we are.
Being full time, we grocery shop at least once per week and what we pick up depends on what we have a taste for at the time. We also pick up local foods (cheese, meat, vegetables, pies) while checking out the area to eat later at home.
I can't suggest a 'best way' for you but I can mention that being flexible makes for a much more enjoyable vacation/life.