Low Adsense Earnings

Hey guys,

I was just wondering to know why my adsense earnings are so low? I had yesterday 80% USA visitors and the rest are tier 2 countries. My cpc was 0.13 and RPM 0.60 EUR

So with 3k visits I earned 1.40EUR

How do I optimize it or does it take time to calibrate or what? I've got adsense 2 and a half days ago…on my other websites i get 30EUR with 2k visits (healthy niche) and here I get $2 for 3k visits (Cryptocurrency news niche)

Am I doing something wrong? How do I optimize the ads?