There is no simple answer which will blow your mind. The only thing we are able to do is offer guidance. Do not over use your effects during a mix. Yeah it may sound cool in the moment, but are you really just substituting that flanger and filter knob for performance? Think about what value this brings to the moment, how this will affect the mood, and does this compliment the current audio track.
We live in the age of the Sync button. Since we no longer need to spend the majority of our time riding the pitch to have a perfect mix, new doors have opened up to creative mixing. For some this means using 4 decks, stems, live remixing, sampling, and creating a full musical performance. For others, unfortunately, this leads to down time which is spent over utilizing what they already know.
Flanger, Echo, Delay, Phaser, and Reverb should all sound very familiar to anyone who is in music. During production these and other effects are used to enhance the sound of an instrument. Lately we have been hearing these effects used more and more in Deejaying. But, what is the right time to utilize your effects chain?
If you are simply trying to find ways to keep or look busy, it is time to expand your knowledge of deejaying. What are the features of your DJ software that you have yet to learn? Do you have any acapella to layer in which could drive the familiarity sense of your set? What direction are you taking?