For mobile, I really have no clue how to subscribe these push notifications, do I need an android phone? for web I already subscribe some push notifications, but I want to subscribe much so I can spy more landing page. need somebody open my eye
Hello wyhgood
What I did, I clicked on few allows inside my Chrome app in my android, and I get few push notifications to my mobile now.
Hope that my info will help 
Browse some movies/torrents/warez sites for a while and subscribe to their push notifications.
Pro tip: if you want to get notification from particular geo, browse those sites with a VPN from that geo location.
Do some recon on whose company is on what site. Subscribe for the big ones: Propeller, MGId, AdMaven(us), Megapush. That would give you a pretty decent amount of push per day from across the board. As erikgyepes mentioned, If you're looking to spy on a specific GEO, do it from a VPN, that way you would get notifications from that GEO.
In general, If you want to know what companies are running you can for instance 2-3 sites of the same company on different site vertical: Streaming, File Sharing, Adult and see what they are running on different verticals from different GEO's. Of course also use a Spy tool like adplexity, Because once a company finds the proper demand it might work for that site, but you might miss out on seeing the rest of their demand. I would focus on one company at a time, just to be thorough.