I have always steared away from giving advice about busking - but as a former Straat Musician here goes.
I enjoyed my times busking when I was young, stupid and full of confidence.
Busking is not a Folk club spot - it is a very limited timescale to catch someone's ear in order to get them to put some money in your bag - much less than one minute - because people are walking,talking and thinking about other things.
Times change, but familiarity does the trick.

Try these at the top of your voice ( especially in Europe ) and if you run out of words - make 'em up !!!

Oh Sinnerman where y'gonna run to,
My Bonnie lies over the ocean ,
What shall we do with a drunken sailor,
Wild Rover.

Don't be frightened to repeat the song without stopping - make 'em last as long as possible - once you get started - providing of course you don't have a standing /static audience.

Yes - they're all shite but they appeal to a wide cross section of people - trust me.

You can sing and play perfectly John Martins "May you never" or Oasis etc and no one will take a blind bit of notice - but give them a bit of shite which they recognise in their distant menory - and you'll do OK.
Ones which don't do OK - drop 'em - and relace with simple songs - sang with enthusiasm.
Essentially - smile - and thank as many people (between lines of verse) as you can.
Those were the days - Oh! - perhaps that's another.
Good Luck.