food has a flavour already, so you don't need to add anything.
If, however, you want to add a bit of variety you can use herbs, spices, garlic, onion, or just flavoursome fruit and vegetables in the first place (as opposed to, say, babyrice)
Steer clear of the chillies for the time being though.
Chicken, meat and fish have very strong flavours of their own, you really don't need to add anything to it at this stage. You may think it tastes bland but your baby wont.
Think of nice fruit and veg that you can mix with the meat, fish or chicken for variety.
Like chicken with chestnut and parsnip
or salmon with pear and carrot
or meat with garlic
Don't bother with the ketchup just yet, plenty of time for them to get addicted to it later on