Stage decks are priced per panel, so the question is really how many panels. Here is the arithmetic.
A solo speaker or a celebrant needs a 1.2 x 1.2m riser — one panel. A duo needs about 2.4 x 2.4m. A four piece band with a drum kit needs 4.8 x 2.4m minimum, and will thank you for 6 x 2.4m. A drum kit alone eats roughly 2 x 2m once the throne and cymbals are out.
30cm is standard and works for most rooms. Go higher only if the audience is seated at round tables and people at the back cannot see. Above 60cm you are into handrail territory, which is a safety question, not a preference.
Skirting so the room does not see the legs. Truss over the stage if anything is being hung. Base plates and weights if you are outdoors — wind gets under a stage and a truss tower more than people expect. And light on the stage, otherwise the people on it are silhouettes.
Panels are heavy and awkward. Before you book, check the loading access, whether there is a lift, and what time the venue allows bump-in. Those three answers change the delivery quote more than the number of panels does.
