Sorry, I'm really not sure what you want to know.
Do you personally want to know if you should focus on your own accent? I'm sure you'd want to present yourself as best you can, so that might be your answer.
Some "foreign accents" come about because of mispronunciation. To be honest, any pronunciation can be learnt, so I can't accept habitual mispronunciation as an acceptable accent. If you say one thing and listeners think you've said something different, then that's an error, not an accent.
English speakers are pretty tolerant when listening to non-native speakers use our language, so in the bigger picture, it isn't a major issue. However, this still depends on the situation - for example, if you represent a company, your language skills need to be of a high level.
What are your thoughts when you hear a non-native Greek speaker? How important is their accent to you? :)