There's no valid reason why you shouldn't try something else, but I want to give you some (hopefully) encouraging advice.
First, four months is very early for solids. I know...it's so exciting, you get so bored with breast or bottle, and you just want to try something new!!! I couldn't WAIT for either of my children to start on solids!! However, at least until six months, all they need for nutrition is breastmilk or formula and even up to a year, most of their nutrition will come from that.
If you want to persist, that's fine (I did, so I'm not saying not to!!!) but steer clear of allergenic foods, such as eggs, wheat, barley, etc. I moved my youngest from rice cereal to barley and wheat cereal around six months and she got very, very sick...and after months of testing, she was diagnosed with Celiac disease. Now, I'm sure that the early exposure didn't cause it and it's not extremely common or anything, but that would be my best advice...skip right to vegetables, or fruits, which are generally not allergens. Skip strawberries, however, and know that citrus can cause diaper rash because a baby's digestive system is not developed enough to handle it.
Some ideas? Bananas, pureed and blended with formula or breastmilk to thin the consistency, can be mixed in with the rice cereal...so can most jarred baby foods. I always did this, and they would eat it. :)