Here's a rough guideline to go by (I tend to make tuna salad with whatever's on hand, so it varies a LOT):
Drain a can of water-packed tuna, and dump into a bowl. Add a couple of hardboiled eggs, chopped, maybe a half of a chopped green Bell pepper, half a chopped red Bell pepper, a couple of green onions, finely minced, a rib of celery, including a generous portion of leaves, finely minced, sometimes a few chopped green or black olives. Moisten the mixture with either a good oil and vinegar dressing, or a few tablespoons of your favorite fat-free Italian dressing.
This makes a good filling for pita bread.
If you like, you can turn this into a dinner salad by adding cooked pasta (rotini, elbow macaroni, whatever suits your fancy). I've also tossed in chopped artichoke hearts on occasion (in which case, the marinade from the artichokes, plus a little vinegar becomes the dressing.
If I want a really SERIOUS salad, I'll also toss in some thawed but uncooked frozen mixed vegetables (the Italian-type mixes are particularly good). Garnish with sliced cucumber, maybe some radish roses or whatever.
Kathy in Bryan, TX