There are many ways to improve your profile before you apply to MS. Here are few things that can make the most impact-
Publish papers for thesis-based degrees
You can work with your college Professors to stay engaged in research. Publishing papers add a whole new depth to your candidacy by showing your research potential.
Freelance projects and build portfolio
Even if you don’t have clients, you can build interesting projects and publish on github. Shows you are a pro-active learner. (can do along with taking MOOCs in your areas of interest). Keep doing competitive coding, any accomplishments in there can improve your profile. Certificates directly don’t matter but participating in such things ensure that you stay hands-on and get to explore deeper concepts of programming.
Read papers on latest developments, connect the dots. You will start talking more intelligently about it. The biggest point where applicants stumble is that they have nothing intelligent to say in their SOP – everyone is saying ‘how they were attracted to computers since childhood’. The more you code, more you explore, better stuff you will be able to talk about. Your goals will be more specific.
Switch to a job closer to your area of interest if possible
One of my students switched his job from a business analyst role to a research based startup in ECE. First time, he did not get good admits but second time, he got into some decent schools for MS in ECE. He headed to UC Santa Cruz. The idea is to proactively push towards your passion. If your job is not helping in what you want to do, look for something more relevant.
Take MOOCs if you lack confidence in your subject
For people who have low grades or relatively less working knowledge of the subjects of their interests, doing online courses (reputed certified ones) can add some more credibility to your academic background. Read how much can MOOCs help you.
Get 320+ on GRE or 710+ on GMAT
Lastly, if your test scores are holding you back, get that sorted. There is no point in being held back if you think you can do much better on the tests. This becomes especially more important if your GPA is low.