No, don't start just yet. Rice has no nutritional value and he needs the nutrition he is getting from formula. How much are you feeding him every day. You can try giving him 6 ounces of formula at this point, depending on his size. More frequent feedings will help as well. He may just need a little more than usual right now because of a growth spurt.
You baby is ready to start eating regular foods when he can use his tongue to move the food to the back of his mouth. This is usually around 4 months or even later for a lot of babies. I usually start giving my babies a start in food around 5 months. I know you are not breastfeeding, but most doctors recommend breastfeeding exclusively for the first 6 months, and I try to do that....lol. But that means that they can live on just formula or breastmilk exclusively for that lone.
When you do start with food, you need to start out slowly with cereal, even mix a little of his formula in the cereal to give it a familiar taste. You will need to feed him when he is not hungry at first so that he will not become aggravated and upset that the only food available is something he doesn't know how to eat yet. Starting solid foods is a learning process.
After he has the hang of watered down cereal, you can mix some of the first steps jars (or your own pureed) veggies and fruits into the cereal or even give him them plain. He will have his own likes and dislikes, so it might take a while to figure that out. I heard that you should start them out with veggies before fruits because they will always like the sweeter fruits more, but I've had babies that like both.
I hope that's enough info for you for now. If you have any more concerns, please ask.