So at first, you start out by saying you need 1 large potato per person. So say you're making potato salad for 4, you add 4 large potatoes... and maybe 1 more for good measure. That's a lot of potatoes. 5 potatoes.
1 onion for every 3 potatoes. So you'll ad 2 onions which you'll fry nicely. THIS IS ALSO DEPENDING ON WHETHER YOU LIKE UR ONIONS FRIED OR NOT. YOU CAN JUST CUT THEM UP AND ADD THEM. If you fry, use 5 spoons of oil or a bit less to fry them in.
I don't use eggs coz it's disgusting... but if you must, I guess 1 egg for 3 potatoes will suffice. it really comes down to how much egg u like. I don't, so I don't add any.
Pickles... why would... why would you add pickles... unless they're those pickles that you keep in vinegar, those small ones, then 1-2 per serving, depending on preference (so for 4 people, 4-8 small pickles), sliced up in that thingy that u can slice them in and that's good.
Why not add something more in there? Like mushrooms. Mushrooms are great with potato salad. Chop'em off in 4 pieces each mushroom and fry them a bit until they lose their water.
When you're cleaning them up, make sure you use boiled water.
Why add mustard... I swear, that recipe is wierd.
Celery... wing it.
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Potato salad is very versatile to do. You can't really go wrong with it. You can improve upon it.
Personally, I suggest you look up potato salad recipes from the germans. they are kings of potato salads and there are dozens of recipes.