When you first start with the cloud wallet, I think they buy you a little bit of RAM. Then they delegate some CPU/NET for you. As for the NET, I have not really needed to stake anything more because it is only for transferring the results of your actions. CPU though is used more often as it does the work for each of your action and you need some more staked if you plan to use the block chain often.
One thing I want to clarify is that RAM does not regenerate over time. It is your storage for NFTs and only restores after you let go of NFTs through sales or burning them.
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