Weaning - 6 months

My son is 5 and a half months and the nurse practitioner suggested he was ready for weaning. She suggested trying cooled boiled water in a drinking cup which we have just done and he’s all giggles and loved it! Just wondering what solid foods and what drinks parents introduced first to their baby? I was thinking just some Aptamil Porridge at one point in the day before his formula for the first couple weeks as he’s only 5 and a half months and start other things in a couple of weeks, I’m not sure. Advice? 😊❤️