Again, how much oil and gas do you think China need in a single year?
And RMB/RUB account is a non-starter, there are no way Russia can guarantee their currency as they pretty much run out of option to back their own currency after US, UK and EU (Together worth 90% of world currency reserve) pull the plug in Russia central bank.
I don't think you have any idea how bad it is, because effectively what the West is doing to is take away Russian central bank to support its own currency, as you cannot back Rouble with Rouble. That is backing something abstract with something abstract. This is not even done to Iran (well, they did it but in a limited sense) and the Sanctioning of NDF is only 5 billions or so, instead of the 300 billions Foreign Currency Russian own overseas.
So basically, by barring US and EU entity to do business in Russia and frozen their Asset in US/EU (including the UK) You effectively block the way Russia can raise fund. Blocking them off SWIFT is one thing (still big on Russia), you stop Russia by buying/selling overseas that uses SWIFT, you can still transfer money using any other mean (CIPS or even direct trade) but stopping Central Bank of Russia from exchanging USD, Euro and Pound, you take away the mean Russia can use to back it's own currency, which mean they only have 1 currency in that basket to choose from. RMB. Which mean either China undercut their own currency policy and move majority of their currency back home to back Russia, which will weaken Yuan, or you print more money (by offering more Line of Credit) to satisfy the trade volume with Russia, which will inflate Yuan. Either way is a bad move.
Gold is a tangible asset. Which mean it's physically thing, so how do you actually back an abstract thing with gold? Say today 1 rouble worth 0.0001 ounce of gold, you cannot change that exchange rate because that would mean "re-cutting" the gold. And there is a certain amount of gold a country can have and there is a limit of abundance. That mean you either overinflate it or you will suffer a slow development rate because you cannot back all the project until the previous one is finished and that gold is "released"
And then you have the civilian ownership of gold. Think about it, if I own, say a ton of gold (which worth around 61 millions USD), Consider Russia central bank only have access to 2300 ton of gold, if I use my ton of gold and go to Russia (61 millions dollar) I effectively own 1/2301 Russian Economy.....(that's 608 millions of dollar in 2021 term)
There is a reason why we move on from Gold since 1914.......