As a general rule of thumb, one or two squirts of washing up liquid should be enough to clean a bowl of dirty dishes. If you use too much, you’ll find you have far too much foam and suds. This can actually make it difficult to find and wash your dishes. Too little washing up liquid, and you won’t get the cleaning power you need.
However, how much washing up liquid you use also depends on the type of product you have. Some types are more concentrated, so you can use less - and it will last longer too. Poorer quality products may require you to use more in order to get the same results.