I will be traveling from Doha to Turkey for 3 days then to Bucharest for another 3 days then Greece for 3 days. Should I get a Schengen Visa from Greece embassy although my point of entry is Romania and not Greece.
If you need a visa to visit the Schengen area (it depends on your citizenship) then you need to get it from the Greek consulate/embassy because Romania is not (yet) in the Schengen area and cannot issue Schengen visas. Romania therefore isn't the point of entry in the Schengen area, Greece is.
Depending on which visa you get from the Greeks, you might also need a Romanian visa or not but you need a Greek visa in any case.