If you practice in codeforces, go to problemset -> sort problem by the number of user solved it -> start solving from first page to last page. Or if that's too easy, read this blog and this. I'm actually facing similar problem with yours. Hope that helps :).

i think solving A and B (div 2) problems is wasting time (not all of B problems) but i think for somebody

that they are not in div 1(like me) solving C and D (div 2) problems are good!

note that looking at Tutorial before thinking about problem won't learn you a lot.

thank for reading! :D