I've been running a crypto blog for a couple of years now and have started to look into ways to monetize it.
I've tried few options, such as referral campaigns for specific sites, but but none have been very successful. Also, it doesn't have a high enough Alexa rank to qualify for sites like MellowAds (top 100,000).
Does anyone have any suggestions? Thanks.
Good Alexa rank means that you have some traffic on your website. There is no ad network which can bring you money without visitors on your site. So I suggest you first to improve your website SEO position and after that, it will be easy for you to implement any ad network.
You are mention MellowAds, I do not recommend to use this service. They relented with the criterion and there is a big chance for you to promote obviously a scam. You may earn something, but in the long run, it's bad for your site.
Maybe you can try with Bitmedia.io, as I know they are not so strict with Alexa rank, but your website can't be fully trash if you want to be approved.
Here is also a few ad networks with Bitcoin payments, but you must check their rules and are you eligible to publish ads for them,
a-ads.com
bee-ads.com
adbit.co
coinadvert.net
coinzilla.com