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
- @Lyn Alden
- Real Vision
- @James Lavish
- @therationalroot
- and many others...

Hope this helps.