Top 5 things to focus on for T10 MBA program?

Let's start with things that you cannot work on. 

That will be your GPA. 

What can you work on?

1) Now we don't know how good or bad your GPA is and in what major. But regardless of that, you need to start studying and get a good GMAT score. I cannot recommend an exact score for your achieve because I don't know anything about you. But in general 700+ for Top 15, 730+ for M7. 
2) Work experience. Do what you like, but be amazing at it. You can be at the most prestigious job in the world, but if you haven't achieved anything or haven't done anything at that job - no one will care. Go out there and excel at your job. Find projects, take initiative and come up with ideas to improve your work. Improve your bosses because they will be giving you an LoR. The better you excel at 1 thing at your job, your manager will give you bigger things to work on, and more and more and more..... You get the point. 
3) Extracurriculars. This is one of the most underestimated things that make a huge deal. This can be split into two things 1) Community Service 2) Hobbies. For community service, don't go out there and work at a local food bank once a month/year. Go out there and do something meaningful. Make a big difference. This is only possible if you want to do it, and not because you have to do it (read that again). Pursue hobbies that can make other things easier for you, such as reading. Reading will significantly help your reading skills and will come in handy in verbal/quant section of your GMAT. Go out and play some sports, esports, pursue something.

4) Network. You graduated from an apeshit undergrad, but stay in touch with your colleagues. You don't know where they will be tomorrow and where they are headed. I went to an apeshit undergrad and I am surprised to see how many other colleagues were aiming for the same goals of going to T15 MBAs. Stay connected. This also goes for your future network. Look at individuals within your current function/industry, your future function/industry. Connect with them. Listen to them about their journey and learn from it. Ask what mistakes they made, so you don't make the same ones. Use LinkedIn! Be professional and do not HOUND. There will be quite a bit of people out there that won't respond to you. Don't be upset, just move on to another one. 
5) RESEARCH. This is critical. Do not be one of those individuals that do not know anything about an MBA, the programs, the schools, future jobs, until the time comes to apply. Know ahead of the time what you want to do. This is variable and things can change anytime, but at least this will help you keep up to date on your goals and research. Example: If you want to do consulting after MBA, research on the schools that have a track record for top consulting employers. Research on types of consulting. Research on the locations. Research on what they do. There is so much information out there on every job! Look up trends on the college applications. You are 5 years out but look at the M7 schools - look at the essays, class profile, employment report for this year. Check the same for next. And next. and next. This will help you see the patterns on what the school is good at, what they ask for in their essays, and the type of candidate they are looking for.

Lastly - be yourself!

Good luck