Hi I am stuck on which one to choose??

I will be flying from Syd to Beijing ---> Air China

Beijing to Hamburg ---> Emirates but not sure depending which is cheapest

Finnair is possible but somewhat more expensive

Then flights depending which is the cheapest option to move from

Hamburg to Prague to Vienna to Paris...

Then fly back from Germany to Beijing

before many domestic China flights...

before flying back to sydney...

More flights around Europe planned for later... this is my flying itinerary for the next 3 month... I only fly economy...

Any suggestions on which alliance is best to gain most use as well as which program to join? I want to use lounges and what not... is Lufthansa a good one?