The main purpose of the dressing is to proclaim the vegetable taste. The secrets to flavour a salad are manifold: all that can enrich the flavour or to colour a dish is ok, all you need to know is some small solutions
Here are some:

The traditional dressing

Oil and vinegar.
The most classic dressing, but what are the right proportions? One spoon of vinegar (traditional or balsamic) versus 3 of oil that has to be extravergine olive oil. The dressing is preferred on the baby leaves a small leave; a robust taste or really spicy for radicchio and rocket.

Oil and lemon
In favour as an alternative to the vinegar and had the advantage to enrich vitamin C salad and renders more iron that can be assimilated in levels and legumes. For the proportions: 1 spoon abundant with lemon juice versus 3 of oil. Also the other citrus fruits are nice such as orange mandarin or lime.

Vinaigrette
La vinaigrette is prepared by whipping salt , pepper, oil, and vinegar in a small bowl making it emulsion the ingredients in one solution. For a more tasty vinaigrette try also to add spoon of mustard.

More tasty dressing

Aromatic herbs
There are a lot to flavour the salad, one of them is the basil, but also the baby onion that gets broken and not cut preferred in green salad, with tomato or fish. The chervil goes with potatoes and egg and the most delicate is the parsley. A salad with good meat also can also be the oregano or thyme.

Mustard
There are different types, for the dressing it’s advised the light one. To make it more sweet and pleasant mix with a spoon of honey or lemon. To dress mix it together with a vinaigrette, then pour over the salad. It’s also good mixed with mayonnaise.

Garlic and anchovy
For who likes strong and resolved flavours a clove of garlic pressed or rubbed in the salad bowl, it’s tasty with the radicchio and gives a more flavour taste maybe adding some anchovies. To keep the strong garlic aroma you can boil it for some minutes.