I recently started learning launching campaigns with landers. I have been searching for the number of a good CTR, but couldn't find information that is really relevant.
So, what makes a good CTR in general?
It's impossible to give you a general number, as it depends on too many factors : GEO, traffic type, lander type, traffic source ... maybe if you specify it more, someone running a similar funnel might be able to give you some ballpark figure.
Judge landers by CR, not CTR.
The only exception is when the CTR is so extremely low such that the math would never work out for the campaign to be profitable (i.e. the conversion rate would need to be impossibly high to compensate for the low CTR).
It's CR and ROI that will make you money, not CTR. I've seen more landers I could count, that had lower CTR but higher CR than the other split-test candidates.
Like matuloo said, CTR can vary extremely widely depending on the factors he listed and more. If you run the same lander in AU vs. EG for example, you may see 1% CTR for AU but 30% for EG. Sometimes just by adding a backbutton script to a lander you can double the CTR. A more extreme example would be adding code to a lander so it'd redirect visitors automatically after x seconds - you would achieve close to 100% CTR then, but it doesn't mean the visitor will go on to convert at the offer page (if they haven't been pre-sold to sufficiently).
Amy