I want to work on a thesis project to analyze demographic changes in Washington, D.C. and show how this could be a result of gentrification. Where could I find the best datasets for this, and what types of tools would you recommend?
There are a lot of datasets available which could be used for a project like this.
If you're doing a thesis, part of your project/paper should be discussing what is the best dataset to use and why.
I would suggest starting with American FactFinder to get some Census data. You can download multiple datasets from that website, which can then be joined to Tiger Shapefiles of the DC area.
If you are looking at information such as Census Data, it can be helpful to view density measurements of attributes.
Look into the different ways density can be symbolized in GIS. A lot of that information you will find in the Spatial Analyst toolbox.
