Your model is learning to do is predict future market data from past market data, which fundamentally is not worthwhile because market data hinges on real-world news. If you want massive quantities of real-world news data in a structured/tagged format, look at GDELT.

https://www.gdeltproject.org/

Also, look at using Kaggle's GPU notebooks instead of Google's. You get 30 hours a week if you verify with your phone number, instead of Google's arbitrary secret heuristic based cutoff. Or look at something like runpod or vast.ai, rates for non secure GPUs are like a few cents an hour and datacenter GPUs not that expensive either.

P.S There are arbitrage opportunities you can spot using purely market data, but those are generally very short-term, don't warrant powerful models to detect and are pounced on by trading bots run by trading firms.