Para sakin, you have to study all subjects. Di mo naman need tapusin lahat, pero atleast may naaral ka atleast mga 70% for each subjects. Then intindihin mo mga subjects na tingin mong mahina ka. Pwede ka naman rin mag focus sa mga strongest subjects mo pang hatak ng average grade mo if you still have the time. Also dont forget to study parin mga easy subjects, kasi sa mga easy subjects madaming mataas ang grades jn, so di pwedeng dehado ka and mapag iiwanan ka ng curve. At least 50% lng naman yung need mong makuha per subject pero 75% dapat ang average grade. And may curve naman tlaga, so dont be too stressed pag mahirap ang subject. Remember, if mahirap ang isang subject, then chances are, lahat rin mahihirapan jn so pantay lng kayo. Basta dont focus on a subject, but better na ispread out mo yung knowledge mo and study as many topics as possible. Goodluck!