Welcome, Amanda! By day 3 you are probably in ketosis, yes. What you are not, yet, is fat-adapted, which takes as long as 8-ish weeks in some people. You can avoid feeling ill while your body adapts by making sure to drink to thirst and by increasing your salt intake (the kidneys excrete more water and sodium when your insulin level drops).
As people mentioned already 20g of carbohydrate a day is guaranteed to get practically everyone into ketosis. Many people have a higher limit, but save that issue for later, once you’re fat-adapted. For now, just play it safe.
As for foods, I love beef (steak, roasts, you name it), pork (especially a picnic, which comes with a cap of fat), chicken (thighs with the skin on, yum!), duck, goose, salmon, cauliflower (especially smothered in cheese sauce, yum!), brocolli (ditto!), salad greens (with lots of blue cheese dressing, yum!)—and God’s greatest gift to the human race (right after coffee, I mean), bacon & eggs.
I love to cook with bacon grease, butter, lard, tallow, and coconut oil. I save the olive oil for salad dressing (too low a smoke point to really cook with) and avoid all seed oils. Sometimes I drink the bacon juice instead of saving it to cook with. Yum! 