Can anyone give me some last minute tips on GRE English section?

Reading section was kind of OK I just needed to skim through accurately
But fill in the blanks and other sections were just ridiculous because almost always, I end up not knowing what the word means
So I always end up guessing the answer..

The only thing I can really rely on is the math section which was really easy
If I get perfect on quantitative (math) sections, does it still look good if I do terrible on pretty much all of English section?

No, it doesn't look "good".
Different schools might weight the sections differently, idk but that's something you should look into. But, unless they fully ignore all of the English sections, yes it will look bad.

If you have trouble remembering what words mean, try reading a dictionary. Or this website: http://freerice.com/#/english-vocabulary/1406