When I bought my first road bike here is what I had invested.

2007 Jamis Ventura Sport-new last year's model $450
Helmet ~$30
Shorts $40
Jersey $30
Gloves $20
Cages and bottles $20
Cyclocomputer $25

Total $615

What I ride today:

I will use my S1 which I purchased used.

Cervelo S1-$800
Helmet $65 my old helmet shattered in a nasty wreck
Jersey/bib shorts $150 This is the cost of my nice Castelli team kit. Do not scrimp on good kit!
Cyclocomputer-$25 just using a cheapo cateye 7
Pump, levers,patches-$30
Sunglasses ~$50
Gloves $25
Shoes/pedals-$250
Total $1395 Total on race day with carbon clinchers...~$2595

Your best money is spent on good shorts with a really good chamois. Don't waste money on a seat pack. Everything should go in your jersey pockets. Metal type cages are junk as bottles will get launched on train tracks or pot holes. I have had better luck with the nylon type.