What is the most important metric for early-stage startup?

MRR, it's all that matters in the first stages. MRR = Growth = Customers. - CAC is not worth it, and you could be spending money to early - CR is something you should track but only important if people truly hate your product(hope you're adding more than the people leaving.) - LTV is only useful if you have data to back it up. In Year 1/2 you're still measuring this and guessing. I would track - Customers talked to each week - How many converted - MRR Weekly To me that's all that matters. If you want to track other stuff, then those would be secondary metrics.