to me the effectiveness is acceptable but not inspiring.
...it brought many new comers...
Thanks for sharing what you
do know. Surely you have a reason for your conclusion "
the effectiveness is acceptable", but is that based on your "gut feeling" or hard cold numbers? From what you presented I would say a mixture at best. It's not an efficient way to conduct an experiment or gain knowledge about your audience or marketing.
When you suggested the idea I was all for it. I was also glad you offered to subsidize the effort by contributing half the cost out of your own personal funds. It was a small investment, a reasonable expense for a trial experiment.
I'll say this, that any marketing venture I get behind and vote for will have to explain how its' effectiveness will be measured. Without that you're just throwing money at a problem and "hoping" it will do some good. It's not a very scientific way to conduct research or run an experiment.
I applaud the initiative and your willingness to use your own funds for it (showing you have "skin in the game" to insure that it works), however I must also say I'm disappointed you didn't have a better plan for measuring the campaign's success.
Live and learn. An example of a good idea that had a flawed implementation. Next time let's apply what was learned from this.