Originally posted by JeffJS Determine a need THEN fill it. That is, If money for the toys is an issue.
I've mentioned this before: For some years I depended on a spiffy Sony DSC-V1. When opportunity (and money) came for a dSLR, I asked myself: What do I want to do, that I can't do with what I have? The answers: Ultrawide, ultralong, and low light. Price and performance drove me to Pentax. So my basic kit are the DA10-17, DA18-250, and FA50/1.4, that I bought with my K20D. I supplement those with a manual set: 16/2.8, 24/2, 85/2, 135/2.5, and 500/8. And other focal lengths for challenge. A mix of wide, medium, and long, fast, and slow. And most of those were pretty damn inexpensive.
If some don't feel a need for long teles, fine. If some want only a wide street lens, fine. I consider everything but the 1000/10 to be street lenses. On a recent long car trip, with 25+ lenses packed, I almost exclusively used the 18-240 (and Raynox DCR-250) and the 16/2.8, with occasionally a 28/2.8 and 85/2 and 200/5.6 (and macro tubes). Yeah, 200mm is a real street lens, great at picking up inaccessible details. Can't do that with 16-24-35-50-85, eh?
Yes, learn just what can be done with one's existing lenses; decide what can't be done with them; then check the budget to see if dreams and desires are really affordable.