This might be an effective strategy, but it sure is extremely boring. Anyway, puppets don't mean gold. All puppets mean are unhappiness. Gold focus and building gold related building means gold. That's why I really hate the mechanic that new cities = dramatically higher culture limit. It is a boring and stupid idea which forces you to puppet, which is excessively dull.
Well, boring is a matter of opinion and after all, "Mace the Ace" wanted to know how to get more gold, not how to have more fun

.
I have to disagree with you when you say "puppets don't mean gold". That's exactly what they mean, well, that and land, science, culture, score and all that good stuff.
If you're having difficulties puppeting and keeping happiness high, you might need to take a look at how you manage happiness. I've never had a problem with it personally. I just prioritize all the social policies that either give happiness, or detract from unhappiness, prioritize city sites (both for settling and puppeting) that have lux before any others and build the relevant buildings. It's not all that hard really.
Also, if you trade post the heck out of puppets land you can often get them to stave down quite a bit to reduce unhappiness. Trade post forest and hills first and they
should (at least they
did) work those in favour of food tiles.
Maybe you enjoy settling all your own cities more than just a few and then puppet through war? I can understand that. I found the puppet concept a bit bland when I first started playing Civ5, but it's not going to go away any time soon, so I just got on with it and learned to enjoy other aspects of the game more.
Maybe there's a mod than get's rid of puppets you might enjoy?
Anyway, I stick by what I said. Puppets surrounded by trade posts are the best way to get high, consistent and reliable gpt. Selling lux/OB etc is fine, but AI attitudes can change and prices can fall. Puppets are always a good source of cash and if you manage your happiness well, they end up contributing to happiness and culture too by building the relevant buildings.