Secret Santa has two failure modes: the joke that doesn't land, and the object nobody wants but everyone must display. Both are avoided by buying consumable or genuinely useful — good coffee, a chocolate box, a proper notebook, quality socks, a small plant, an olive oil, a gift card for the café near the office.
Read the room on the cap. Most Australian workplaces set A$25 or A$30, and going well over it makes everyone else's gift look thin. Going under is worse.
Safe-for-work test: could it be unwrapped in a room including your manager, someone you've never spoken to, and someone from another culture? If any answer is no, choose again. Avoid alcohol unless it's explicitly allowed, avoid anything about appearance or diet, and avoid personalised in-jokes when the draw is anonymous.
Delivery: buy by the first week of December. Office parties are usually the second or third week, ahead of the postal cutoff.