Advice regarding a side project idea?

I am a new developer and I am still getting the hang of it so go easy on me. I was wondering to build a smaller version of a web app like https://gocdkeys.com/en where I can compare prices of games where it gets the prices of a game from different stores. How would I go on about this, what are all the things I would need to learn to do this? Any type of help would be appreciated. Thank you