HI Pravin,
3000 alphas does not surprise me.
There is public evidence that WorldQuant and other firms generate these alphas with a machine. (The WC founder published a book, I can point to three interviews where people managing over $1B discussed using machines to generate alpha signal. )
As these large quant funds have access to similar tools for automating the alpha creation process, the differentiator is alternative data. You listed some sources there, but the big funds want data that no one else has. They have teams with multiple people trying to find new data sources. The workflow is something like: 1. get data, clean attach ticker, etc. 2. Generate potential alpha signals 3. look at Information Ratio of alpha signals using something like Alpha Lens 4. build real strategy (AlphaLens does not consider trading costs, slippage, etc.) 5. Evaluate out of sample
Quantopian provides a lot of stuff for free, so do the best with what you have. If you want to trade other things, and other data sources you can use Zipline the open source tool that powers Quantopian.