You can use whatever data you want. But here are a few sources which could help you to get started or give you new ideas 👇

• OpenStreetMap
  • OpenStreetMap (OSM) is a collaborative project to create a free editable map of the world. If you seek for easy ways to get an extract of the data, you can check for GeoFabrik for Shapefiles or Overpass API for GeoJSONs etc..
• Overture Maps Foundation
  • OMF publishes global data extracts monthly which are a combination of OpenStreetMap and other open data sources.
• Natural Earth Data
  • Natural Earth is a public domain map dataset available at 1:10m, 1:50m, and 1:110 million scales. Featuring tightly integrated vector and raster data, with Natural Earth you can make a variety of visually pleasing, well-crafted maps with cartography or GIS software.
• Free GIS Data
  • The site contains a categorised list of links to over 500 sites providing freely available geographic datasets - all ready for loading into a Geographic Information System.
• OS OpenData
  • Ordnance Survey Open Data for Great Britain. Includes general topographic map data at a range of scales; useful thematic data such as greenspace, terrain, roads and rivers; postcode and place name georeferencing.
• Humanitarian Data Exchange
  • Interesting datasets from around the world.
• LINZ Data Service
  • New Zealand land and sea data available for free under a Creative Commons licence via download or OGC APIs.
• LINZ NZ Aerial Basemap
  • Current aerial imagery for New Zealand available under a Creative Commons licence via WMTS or XYZ tile services.
• Open Topography
  • Lidar point cloud and DEM data.
• A collective list of free APIs for use in software and web development.
• GIS data repositories spreadsheet by Karen Payne
• Data is Plural
  • The best data newsletter out there with an awesome archive including also some very obscure datasets.