In my experience, the key is groups and subscribos. People don't make many advance plans in SL, but if they are online chances are they'll be looking for something to do. When your event notice comes into their browser a few of them will join you. Last month there were some technical difficulties with the subscribo at the club I co-own, and the number of people at the shows dropped off dramatically.
As you are just starting, I would look for a DJ with a large following. Expensive? Possibly, but if you are serious about doing this then its an investment. Then let people know that if they like this DJ and enjoy this event, you have similar fun events on a regular basis. Encourage them to join your group or subscribo to receive notices of future events. Then do not spam. You have to find the balance between letting people know what's happening and not annoying them. Then deliver on the promise of fun events.
Are there groups for Techo-lovers from Germany or Clubbers from France? A group who wants to re-create the London party scene in SL? Can you join these groups? Can you let the members know about your great new club, and the special event you're having with DJ BIGDEAL starting in 5 minutes?
Post a clear listing in the events section of search. Target the people who are looking for the type of music and atmosphere you provide. Not just "DJ BIGDEAL!!!!!!! Live at NEWCLUB!!!!!!!!!!!" Something that tells me what type of music, what type of club, what I should wear, etc. If its all about the music, let me know. If its all about meeting people while music just happens to play, that's ok too, but let people know.
It will take a while, but if you're around for the long haul you'll cultivate a group of regulars. You have an advantage having shows in European-friendly times.