This GentriMap comes preloaded with Berlin data for 2007 to 2011. See in context at gentrimap.net.
Customise it to include your own data by adding your own topojson and csv files to the _/data folder.
index.html and gentrimap.js are heavily commented with more instructions.
To show a different data analysis, you should adapt the function setnineclass() in gentrimap.js to add your own classes to the city districts.
If you add the same classes to your key/legend, (see #map-legend .colours) then the hover and click interactions should continue to work as before.
To change the css, you can either edit the css/screen.css file directly, or use the SASS files. You can run compass watch on the _ directory. Bootstrap 3 and Leaflet CSS is included.