Hard Earned Adsense Earnings

After 5 months of exploring Google's Adsense, I have only managed to make a paltry sum of $21.85.  

It does provide me with a source of passive income though of roughly $4 per month which beats a $10,000 deposit in a bank earning a low interest rate of 0.25%.

However, the low adsense earnings is still not sufficient.  

I need to find other engines of growth to make my adsense earnings grow more.

Perhaps I will concentrate on a single site that will generate sufficient traffic to provide all my adsense revenue.