is it advisable to first master topics which are easy for us or the topics which are diffcult for (as easy topics can be done ltr in less time)??

Hello student its prefer to cover tough topics first and then move to topic which seems easy for you. Once you're done with tough topics then you've to spend a little amount of time on topics which are easy so try to cover tough topics first. Once the examination are close then don't study new topics cover all the topics you've studied earlier and practice as much as you can.

Feel free to comment if you have any doubt
Good luck