What's the "oi" for again?
"οι" is the nominative plural for masculine and feminine nouns. Check out the Tips & notes by clicking on the light bulb image for the Basic 1 skill.
And sorry we didn't see your post sooner.
should ο γυροσ και τισ πατἀτεσ work too? not just ο γυροσ και οι πατατεσ?
Since the word "και" connects the two nouns, the cases of the nouns should match. Therefore it should be either "ο γύρος και οι πατάτες" or "τον γύρο και τις πατάτες"
No, τις πατάτες is the accusative case and this sentence needs the nominative case οι πατάτες.
But if you eat this dish, you say [Εγώ/] τρώω τον γύρο και τις πατάτες
Why is accusative used for I eat gyro and potatoes
A gyro is not a γύρος as far as im aware. We'd normally say gyros.