Analytics-Vidhya's Big Mart Sales Prediction
It is a good competition to understand the role of data preprocessing to get a good rank in data science competitions.
The link to the competition is here.
The complete GitHub repository can be accessed here.
I have explained my approach to data preprocessing here, set up the cat-boost model here, and tested other models here.
By this and setting up a simple model without hyperparameter tuning, I was able to be in the Top 1 % of all participants. (RMSE = 1148)
If you are new to data science, after going through these notebooks you will be in a good space to participate in various data science competitions.