I started my baby on rice cereal at 5.5 months. but bear in mind that different babies may start at different stages so you should see whether your baby is ready to start on cereals. If she refuses it profoundly, don't push it, just drop it and then come back to try again in a couple of weeks time. Some babies don't like cereal and was fed on milk for a fairly long time, tried cereal but failed and then the mother waited until baby is old enough to eat congee and then these babies go straight into congee without the cereal stage. But each baby is different so you must observe how your baby react.
i tried different brands (although all organic), such as earth's best (this is not bad but the problem is it will become very watery if your baby is a slow eater - can buy from citysuper and large Park N'Shop and I think some welcome also has it), organix (I personally don't like the texture and my baby dislikes this the most amongs all the brands I tried) and also PIPPS (you can buy this from bumps to babes at 5/F Pedder Building in Central and my baby likes this best. Easy to mix and does not become watery easily.)
But you may need to do some experimenting to see what your baby likes. My baby hated watery food as he grew older and hence the search for cereal with different texture on my part.