Welcome
like they said: you should really try GWX (put patch the stock version first!) and then patch GWX too.
More important than how much renown is: how much trouble for how much renown?
For example: many don't find small ships like tug boats, small merchants and such worth a torpedo, and save their torps for the big targets (if they can find any). But that's something you have to decide and experience for your own.
Good hunting!!