It depends what you mean by "best."

I use a TradingView algorithm, which is directionally accurate, but requires a subscription (I think).

The FRED (St. Louis Fed) site tracks US M2, although I prefer global M2 for global assets, like bitcoin.

Many people/sites regularly post updated global M2 charts, including:

- Michael Howell (Cross Border Capital)... the most nuanced and complete

- Darius Dale

- Hedgeye

- BM Pro