As I understand it the idea that Greece was unprepared to enter the EU is a myth - at least in financial terms.

What happened to Greece is is something I believe the EU as a community should be ashamed of.  At the time of entry its economy was in surplus and their national debt was non-existent. 

Once in the EU it was 'pressurised' to modernise its industry and infrastructure - German and French banks fell over themselves to lend Greece vast sums which ended in Greece's debt rising to unsustainable levels alongside a budget deficit and a level of consumer debt not previously seen in Greece. 

When the banking crisis occurred and Europe went into recession Greece could no longer service its debts resulting in what we've all heard about, a financial bail out for Greece.  Greece didn't see any of that money though, it all went to the French and German banks - so it wasn't really a bail out for Greece but indirectly for the banks - the conditions attached to that bail out fell though on the Greek population in terms of austerity measures and not where it really should have fallen, on Germany and France - Greece will for decades continue to support the banks of two of the richest nations in Europe.

As regards to EU contributions the highest contributor in percentage terms, (contribution as a percentage of gross national income), of all the nations in the EU is Greece!