I am tempted to start looking into the macro photography but I do not want to invest to much into it.
So, I'd like a cheap solution, like Macro "filters" OR some extension tubes.

Q1: how does each tool influence the photo quality (the sharpness), if it does?

Q2: what would you recommend and why?

Q3: what's the difference between different extension tubes?
Why some are cheaper than others and, what should I look after when I'll buy one.

Thanks!

A nice video about this but, without so many details