First listen to some advice's here it could help you a lot. Second follow some of the @DdmrDdmr topic about merit and merit distribution, and look where is most given section for merit. He have very good explanations and tables with this. Start from there you will see that you could get some point in where to get it and on which topic you can be good, maybe good.

If you want to see something good follow his steps then (i mean on DdmrDdmr) he has already enough merit for legendary.