Dubai is neither Japan nor America. If you go with 10-12% in a restaurant you do nothing wrong. In most restaurants service charge us included anyway so no need to top up extra on that.

Otherwise if you like an uber driver / house keeper etc btw 10 and 20 Dirham should do it (£2-5) or a more if you driver longer (say from DXB to JBR).

If you have a guide for a day or a few hours feel free to give the equivalent to say £20-50 really depending on hours spent.