Lego

Some pieces are pretty rare and you can likely search for sets that just include those specific pieces, but it is admittedly hard to quantify what's rare if you don't know Lego.

As an example though, the larger minifigures like you have right in the middle were not common at all, you're looking at maybe 5-6 potential sets at most for that guy. Searching for the more standard minifigures will probably put you on a good path too, parts can be mixed and matched, but the chest pieces will likely be the rarest items. Extra large pieces like the boat piece the person on the side seems to be holding are another good option.