Welcome to the Bunnings Workshop community. It's superb to have you join us, and thank you for sharing your question about anti-slip coatings.
Would it be possible for you to post pictures of your terracotta tiles? This is to give our members a better idea of what it's like. We can then offer an effective solution to the slippery surface. If it's a flat surface, I often recommend using DTA 1L Anti Slip. But, if it is an uneven surface with dips and valleys, we will need to see it first, so we can make an assessment.