Shirotama, in what percentile were your GRE scores? The good thing right now is that many institutions are not requiring GRE scores, in part because of COVID.
Other than GRE, in order of priority, I would recommend that you increase 1) research lab experience (even if it means volunteering), 2) publishing some of your previous work, 3) presenting some of your work at a local or regional conference. It does take some time to build a strong CV, but getting these experiences can really go a long way to show that you are a highly qualified candidate.
I would only worry about the GRE if it is required and if you were below the 50th percentile. Hope this helps.