This is not meant as an offence, mate: I can't believe that you didn't know about those. I've been using them for like 20+ years - my father taught me how to fix flats - he had been using those patches before. We never bought tubes - just patched them. If tyres aren't too thin (like 23 mm ) - you can patch them 20+ times without any difference in ride quality.

The only time I got a spare tube was when I was older and started riding 100 km away from home - just in case.