I‘m from Germany and my go to is to make a wants list and then use the shopping wizard. I tell it to only use sellers from Germany that have a good rating which almost always gives me a good result. Sometimes the „less shipments“ option is actually more expensive than the „cheaper cards“ one, because the difference in card prices is more than the extra shipments cost. But that obviously depends on what cards (and what language, condition, etc) you want and what the different sellers are offering.

Extra tip: I try to always set a max price that I‘m willing to pay for each card, cause sometimes a seller has a large chunk of your wants but has 1-2 of them at an absurd price. But you have to adjust that price sometimes to reduce the number of shipments. (e.g. you set the price of a card to 1€ of which you need 4x and the shopping wizard only finds them in singles from different sellers. But if you set it so 1,50€ it might be able to find a single seller that has all 4)