If your equivalent GPA is 3.5 or over, you are in the academic range for some top programs. At the same time you are under the average years of work experience for most programs. Starting your own venture, you will want to demonstrate your leadership and maturity through examples of what you did to found and grow the company. Make sure that you refine your career goals so you are clear on where you want to go in the short and long term. You want to have a foundation of experiences for this path to make sense and for your short term goals to flow into your long term. You also want to be clear why you need an MBA at this point in your career. You have some good extra-curricular activities, but make sure you are focusing only on ones from within three years of when you apply.
In terms of schools, I suggest you think about what you need to learn in an MBA program which will be based on where you want to go in your career. Then think of your other criteria (geography, program size, teaching style, etc) to find the right fit for you. You may also want to look at programs that typically accept younger candidates such as Kellogg.
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