Ideally you would have taken that first test a few weeks ago, but anyway now you have a sense of what the test is actually like and where you stand.
It sounds as if you took a GMAT Prep test. That would be good, as of the available practice tests, the GMAT Prep tests are most like the real thing.
Now you can go back over that test and basically see what you need to learn in order to score higher.
Anything you didn't know how to do or which took you a long time to do is a clue pointing you toward an area to work on. Each time you get better at handling questions of a type, theoretically you are going to score higher next time you take the test. So, you can drive your score higher by working on one topic at a time and, basically, driving your score up point by point.
As you do this, I recommend taking practice tests more regularly than you have been. There are multiple reasons for doing this. One is just to get better at handling the test itself. Another is to see how your progress is going.
As far as SC goes, be sure to see SC not really as an English test but more as a reasoning game. Yes, learn some rules, but don't get too caught up in them. You need to get good at seeing what a sentence actually conveys and at analyzing the entire structures of SC answer choices to see which is the best.
By really going at it you could significantly increase your score. You didn't say what your goal is, but by getting around six more questions right in each section you could conceivably increase your total score by 100 points or more.
If you want more ideas, maybe you could provide some more information, such as what areas of quant or verbal you feel you need to work on or specific types of challenges you are experiencing.