People look for:
a) food
b) clothing
c) cardboard, jars and other things they can turn in for recycling and receive money in return
d) something of value that somebody accidentally dropped in the garbage - jewellery, cash...

They do it at regular intervals during the day and they are often accompanied by stray dogs. But in these case these dogs are not really stray, are they?

They are not concerned with the person you are. They are concerned with what valuable things they could find in the garbage and they are concerned to find them first. I am most sure that they don't think about you in particular and that they don't analyze you. I can only imagine that they have seen far more shocking things than the results of the ordinary life of one young woman.

Finally, when I decide that I don't want to wear one particular pair of boots anymore because I don't like them but they are still usable I just put them in a separate bag and in 15 minutes they are gone from the garbage dumpster. You could do the same. Both recycling and clothes donation are not very well organized in Bulgaria. Or they are organized but through this means.