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Better to think about not spending than about earning.
Literal
Earn thought [than-より] not-use thought.
A compact proverb with no main verb — two noun phrases joined by より, implying 'Y is better than X.' 儲ける ('to earn, to profit') is contrasted with the classical negative form 使わぬ ('not using,' an older form of 使わない). The combined wisdom: saving what you have is better than straining to earn more. The classical ぬ gives it a proverb-style antiquarian flavour.