Welcome to the Bunnings Workshop community. Thank you for joining us and sharing your question about priming before tiling.
It is always good practice to prime tiling surfaces whether old or new. I recommend giving the floor a good wash to remove any dust to prevent tile adhesive failure. Once the floor is completely dry, I suggest using Dunlop 4L Multipurpose Primer. A four-liter bottle covers approximately 24 square meters.
Let me tag our experienced members @JDE and Adam_W for further advice.