One modest income and no kids quite yet. I have a bit of liberty, but it took me 2 years of riding before I was able to justify spending 65 dollars on a pro fit, which I just did yesterday. Other things have come and gone, but something as important as fit should have been done a long time ago.
My priorities go like this.
1. Anything needed for safety/comfort on my wife's bike. (gotta keep her happy)
2. Maintenance parts on my bike (i.e. cables, bar wrap, chain, tires etc.)
3. Cycling clothes.
Much beyond that and I feel like I need to search the house for things to sell in order to buy something new. I probably need to replace my cassette, but it's on hold, and I've rotated my tires once and they both have a flat profile by now. It's the tires and chain, the stuff that quickly wears out that I hate spending money on. It reminds me that this can be a tough sport for a poor man.
I do as much work on my bike as I can before taking it in, and help friends out as much as I can to tune/fix their bikes for the practice. I have one old kit that I barely use, one new kit that I wash a lot, and 2 pairs of socks. Everything else like Helmet, sunglasses, gloves, arm warmers, shoes etc...were part of my initial investment and will have to last me a long time. Once my wife gets out of school we'll have more breathing room.
-Jeremy