How do you buy more rmb as investments?
Go to some Mainland China's bank available at your local city and open a CNY account there, then do saving in CNY or RMB
but I prefer to suggest you to buy some physical gold to hedge for longer term, 5-10-20 years proposition; also keep in mind that China is a huge exporter nation, having overly strong yuan is not something China prefers, just maintain a stable currency is their intention. I myself ain't so eager to save in any fiat currency, just maintain some for living & some extra... then allocated into real/hard assets (paper assets are worse than fiat currency: stocks, bonds, insurance investment, paper gold, anything based on promise/fiduciary, etc), gold bar should be in the portfolio in significant amount, but again for longer term outlook, not for short term buy-sell gain. But now the world is changing fast, on the crossroads, so decision must be made quickly if have not... when thing is clear cut, it's already fixed and it's too late for us to jump in the wagon, train already left the station.