"however you can have a list of tracks to be played during the gig"
Thats what I did in my last party

I made a list of tracks, with their BPM, so I can mix easily
playlist never works, you should play depending on the dancefloor mood.
Tiesto played "Forever Today" as "encore".
But some DJs plays the same song twice & even more, which is a really bad idea, even if its a good song , & some people who knows nothing of DJing, they will have bad thoughts about him.