The key to this answer is identifying who are the most important people to build relationships with. The answer cannot be everyone - this is a firm of thousands of people, so being selective about who you are identifying is important.
One key element of this is thinking about what is the purpose of the relationship - how will you benefit from that relationship existing?
Then think about how the relationships with those different people would differ and therefore how you may look to build a relationship in different ways.
Finally, feel free to put your own individuality on it. If you are interested in a particular practice area or want to be part of an employee network group, your answer may have more elements of that.