How much should I pay for expense ratio?

Good day, I'm curious about the ideal amount one should be paying for an expense ratio when investing in cryptocurrency or other financial instruments. Is there a general rule of thumb, or does it vary depending on the specific fund or investment vehicle? What factors should I consider when evaluating the expense ratio of a potential investment? Are there any potential drawbacks to opting for a lower expense ratio, or is it always better to aim for the lowest one possible? I'd appreciate any insights you could provide on this matter.