Dear Proud Mama,
I know you get sick of hearing this, but there really isn't a right answer because every baby's different. Basically, though, doctors say that until he's a year old, breastmilk is still going to be your baby's primary source of nutrition. That means that the supplementary rice cereal and stuff you're feeding him is more for practice and taste enrichment than it is for nutrition, especially for the first several months.
I would certainly never set myself up as the authority on all things baby, but I have now managed to keep a child alive and thriving for over a year, so I'll tell you what I did.
We started with rice cereal at around 5 months. I gave it to her about 3 times a day. I would feed her a little bit of cereal first before nursing. Let me tell you, babies know the difference between cereal and breastmilk, and when they've had enough cereal and are ready for milk, they make no bones about letting you know. They'll just refuse to eat the cereal, and/or scream and fuss if you try to force it on them. Don't be worried about your baby filling up on cereal so that he denies himself milk. It won't happen.
As far as giving other foods, we just kind of played it by ear. When she first started eating the purees, one jar would last for several feedings (I mixed it with the cereal.) Soon, though, she'd finish one each sitting, so I'd give her a new kind each meal. Sometimes I gave her several tastes of different kinds at each meal; sometimes I didn't. I played it by ear depending on what she'd eat and what food I wanted to get rid of. Again, it honestly doesn't matter that much, because milk is still going to give him all the nutrition he needs. Also, while it's a good idea to give him a variety of foods, don't freak out if he doesn't like certain foods - it doesn't mean he's destined to be picky. Despite my many attempts, my daughter would not eat pureed vegetables. However, now that she has teeth, she eats them readily in non-baby-food form.
As far as how much to feed, give your baby as much as he's willing to eat. Again, you'll know he's full when he just refuses to eat any more. As long as he's continuing to dirty his diapers regularly (liquid and solid), he's getting enough to eat. (By the way, get ready for a change in smell and texture in that area.)
It might also give you confidence and direction to check out Gerber's feeding advice
. I printed up a couple of their proposed menus to use as guides. It actually didn't change the way I did anything, but it helped to reassure me that I was on the right track.
Good luck - you'll do fine.
The Cleaning Lady