Even when I was first starting I never bought kits. I found recipes in books or online and adapted to what I liked. It's very easy to do. As for pricing, I looked at Northern Brewer's web site for a simple ale along the lines of what you were asking about. They have a SMaSH recipe that sounds...
I have, as well as using the Mr. Beer LBK (2 1/8 gallons) with my own recipes. For scaling a 5-gallon recipe down to 3 gallons I just multiplied the grain and hops by 3/5. It doesn't hurt to run the answers through a brewing calculator.
I would also suggest simple to start. An extract pale ale is hard to beat for this. A few pounds of LME and/or DME, a couple of ounces of hops and a packet of US-05 will make a fine first beer.