Some very good advice above. Yes, think hard about what you want. But remember that good judgement is a result of experience, and experience comes from making bad judgements.
My mantra is, ASK YOURSELF: What do I want to do that I can't do with what I have? Before I bought my first dSLR, the answers were: wide, long, fast. Nobody else had an affordable great fisheye 3 years ago, so the DA10-17 drove me to Pentax. My first kit had no kit lens: K20D, DA10-17, DA18-250, FA50/1.4, AF360. Then a Raynox DCR-250. And 300+ lenses later (110 sold, 210 kept), that's still my basic kit, although I now use the Tamron 10-24 more than the DA10-17.
The next step was to get faster lenses at critical focal lengths. MFL's were/are affordable; AFL's, not so much. This led me to 16/2.8, 24/2, 28/2, 50/1.2, 55/1.4, 85/2, 100-105/2.8's, 135/2.5, 200/3.5, etc. Those faster lenses get the most use now. But along the way came intermediates: 24/2.8, 28/2.8's, 35-37/2.8's, 50-55-58/1.7-2's, 135/2.8's, etc. And slower lenses with 'character': 21/3.8, 35-40/4.5's, 100/4.5's, 180/5.5, 200/5.6, others.
Then came the bellows and tubes, and sticking enlarger lenses (EL's) and projector and copy and xray and MF/LF lenses onto extension for both macro and general photography. And next will come a Sony NEX with the ability to use zillions of cheap fast cine lenses. LBA doom, that's what it is!
I didn't follow a roadmap. First I knew what I wanted to do, and I got the necessary tools. Then I found I could get zillions of great (and some not-so-great) old manual lenses real cheap, and I started a lens lineup, and then of course I had to fill the holes in that lineup. Alas, there's always another hole... But my total investment has been less than the cost of a beat-up used car or a decent Navaho rug. (And I had an inheritance to jump-start my LBA!) So it's no financial burden.
But it boils down to: Decide what you want to do, and what tools will help you do that. Wide, long, fast, close; idiosyncratic, invisible; flexible, specialized; etc. They're all out there, and some are amazingly inexpensive.