Hi Charlie,
Most if not all the sites you have mentioned provide a public API for fetching data.
For example Deviantart’s API can be found here Developers | DeviantArt
Typically, accessing API’s is done by calling fetch()
See more information regarding fetching data from 3rd party services in the link below
Once you retrieve the data, you will have to create a function to eliminate duplicates before adding it to your main data collection.
A word of caution: The system you are describing is quite complex and will be a challenge for beginner coders.
Feel free to post any questions here.
Good luck!
Ido