Developing community in an apartment complex setting doesn't necessarily mean it's harder than if you're a homeowner in a neighborhood. Many neighborhoods are inhabited by renters and occupants can come and go throughout the year. Some homes are rental homes, and some are lived in by the homeowners.
The advice that I would give to an apartment dweller would be no different than what I would give to a homeowner. Do your best to get to know your neighbors. You don't have to include your neighbors in your inner circle, but it is important to have an idea about what kind of people you are sharing your foxhole with. Who are potential problems? Who can you build trust with or turn to if you needed? Even in apartment complex living, there are folks that are long-term residents. I would seek those individuals out and get to know them too. Most likely, they are home most of the time and will have very detailed information about the comings and goings of the complex. You don't have to make everyone your buddy, but having an idea of the sort of folks you're dealing with in your immediate surroundings is very beneficial.