LOL! I love the Disney princesses. I have an Ariel someplace. No other Barbie Disney princesses, but I have a Wonder Woman Barbie which I treasure (I also have a DC Superhero girls Wonder Woman doll which is awesome too. I have plenty of Wonder Women. One of them was a gift from 3 people of this forum.)
We have the four-leafed clover too and the breath on the dice. We just touch wood (3 knocks sounds familiar but it is not necessary) when we want to prevent a jinx. Like when you say that all is going very well and then touch wood so not to jinx it. A twist on that tradition is that said wood cannot have legs, so you can't use a table or chair, you have to find a door, wood wall, shelves...)
I remember red things against the Evil Eye, white rabbit legs, a couple of decades ago everyone here had small red horns (like from a bull or something) trinkets "against envy".
Bad luck
Open an umbrella indoors
Walk under a ladder
wishing someone "happy birthday" because the actual birthday
Number 13, specially Tuesday 13 (yes, not Friday. Tuesday)
My family said there was also bad luck to have you measured (as that is what the funerary person would do if you die, to have the casket done for you). So you were supposed to use a ribbon or something to have your shape and then you measure that ribbon. But my husband family had not that tradition, so I don't know how spread it is.