Aw don't worry, normal yan especially kung medyo late sya mag-start, some babies take a few weeks pa bago ma-adjust sa textures, kaya walang pressure! A few of us here had the same experience, one mum friend's baby took almost two months before she accepted anything other than milk, tapos biglang okay lang lahat haha. Since he's doing okay with cereal, pwede mo try gradually mixing it with very tiny amounts of mashed fruits like banana or avocado (super soft talaga), or introduce other cereals first (rice, oatmeal) para may variety, pero honestly, if he's thriving and gaining weight, cereal is perfectly fine while you're introducing other foods slowly. If the gagging and vomiting continues with everything else or you notice something off weight-wise, worth checking with your pedia kasi sometimes there's a tongue-tie or texture sensitivity na kailangan address, pero mostly babies just need their own time, mama, you're doing great!