Hello Prashant, Blogging is one hobby which has been turned to a full time work/source of income by many since the internet revolution. Its good that you have passion in it and want to turn it into a full time work but it has no relation to what course you will undertake.

All the courses you have mentioned would require certain level of dedication to excel in, with or without your blogging activity, now Economics or Finance or history be it BCom or BA, all are serious subjects that would require you to put in lot of effort. SO make sure you choose whatever INTERESTS YOU THE MOST.

If your blogging is related to any subject stream then better go for a degree in that subject since it would only aid in your gathering of material to be published on your blog. There are plenty Bloggers who study Physics/Maths/Chemistry and run Science Blogs.

Hope you understand.