Is this possible? I know you have to convert it to JSON and the publish it. Is there any examples/guide out there?
If you want to publish the whole file geodatabase, just zip it up and publish as shown here: Publishing SDs shapefiles and CSVs | ArcGIS for Developers
If you want to publish just a subset, then you can read it into a SpatialDataFrame (arcgis.features module — arcgis 1.4.0 documentation) filter and keep just those features you want, then publish that as a feature layer. Check out the first few lines in this example: arcgis-python-api/LISAMap.ipynb at master · Esri/arcgis-python-api · GitHub
Retrieving data ...