My breastfed baby girl started on solids when she was 4 1/2 months old. The guidelines I read and was told about by my pediatrician said that babies can be given baby cereals and other 'solids' as early as 4 months without a problem. We started her early because she was getting fussy at mealtimes and reaching for our plates and doing mouth movents that indicated she could start swallowing food. I bought the book Super Baby Foods by Ruth Yaron as a guide to make sure I introduced foods in the proper order.
I kept reminding my self that early feeding is more about learning how to eat rather than getting nutrients. My daughter loved to play with her spoon and spent a lot of time just exploring the food in her mouth. It was a bit messy but she picked up quickly what was going on. She is now 12 months and loves meal time.
My daughter wasn't fond of baby cereal at first and didn't like anything I mixed with breast milk. She only likes her breast milk straight up ;-). Oh, and at 12 months she is showing no signs of weaning and is probably drinking at least 12 ounces of breast milk.
Her early food favorites included sweet potato, banana and peas. I made all of her food initially and thinned them with water. Have you tried making it yourself rather than using jarred food? My daughter is picky when it comes to the quality of her food and won't eat jarred versions of food she usually likes. In fact, she won't eat generic frozen veggies. She will only eat them if they are fresh or a more expensive brand.
Good luck with the feeding.