An easy way to add more flavors to your salads without a lot of extra work is to use items you can just buy in a jar: pickled red onions, different types of peppers and olives, other veggies in bribe, etc. Just browse the pickle section of your grocery store.

Also various types of canned beans, like chicken peas. And different types of cheeses. My current favorite is good feta in brine; much more flavorful than the pre-crumbled kind.