I am new to adsense please tell me how much 300x250 ad unit i can add in per day or which ad units give more earnings?
No one will have any idea with out knowing your site and your traffic patterns! Best thing to do is to do some testing yourself.
Easy to find out just using a simple Google search. https://support.google.com/adsense/answer/1346295?hl=en-GB#Ad_limit_per_page
It tells you what you can use if you read the bloody link, can you read or are you just inflating your post count with pointless questions?