It all depends on where you go. Using ham, egg and chips, you're likely to find that the ham could be free (assuming it's plain and doesn't have a glaze) the egg is likely to be cooked in some oil, even if a little bit, so I would count maybe 3 Syns to be safe, and the chips can range from 9-14 Syns per portion
If you're eating out and went to keep your Syns low, I always suggest a grilled piece of meat (gammon, chicken breast, steak) with either salad, jacket, new potatoes, veggies (without any butter)
You can always ask the people at the places you eat how things are cooked, eg how much oil is used, if any at all.
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