Budget travel in Athens

I'm getting there in a month with a friend, we'll be there for 4 nights and 5-6 days (tuesday morning to saturday evening). Our nights and flights in and out are covered already. We have planned a few activities that don't count into this budget.

Mostly wondering about the cost of food (eat out lunch and dinner, breakfast and snacks from grocery stores/markets, not interested in expensive or fancy places) and travelling inside the city (public transport). How much do you think we will need minimun in a day if one meals is gyros or something on the cheap side and the other is "bigger real meal"? How much does alcohol cost in stores and can it be bought in normal grocery store?

Also where can we get, if be buy the 5 day public transport ticket. Does the ticket include only the close center of Athens or can we get to Glyfada or even Vouliagmeni? How can we get to Sounion and maybe beach near to it? If we can't get to Sounion with publich transport, what is the furthest we can get and maybe get a taxi from there?

Is there anything I should take into account? I have been there in 2018, my friend never, so I know some places but if you have suggestions for alternative, weird or different kind of places to go eat, drink or have a caffee?