Hello,
While I certainly agree with the positive comments about the EF 17-40mm f/4L USM and the EF 70-200mm f/4L USM lenses, they are in a different price class than the kit lens and the thrifty fifty.
I always tell folks who are shopping for Canon lenses to narrow their selection to lenses that support Full-Time Manual Focus. These lenses tend to be a bit better made than the more entry level, plastic mount lenses. For example, here are some FT-M lenses that are less than $400 US at B&H:
EF 28-105mm f/3.5-4.5 USM $230
EF 100-300mm f/4.5-5.6 USM $280
EF 24-85mm f/3.5-4.5 USM $310
EF 50mm f/1.4 USM $315
EF 85mm f/1.8 USM $340
EF 20-35mm f/3.5-4.5 USM $370
EF-S 60mm f/2.8 USM Macro $385
EF 100mm f/2.0 USM $390
EF 28mm f/1.8 USM $400
From the list above, the EF 28-105mm f/3.5-4.5 USM and the EF 100-300mm f/4.5-5.6 USM would give you more than a 10x zoom range with metal lens mounts, USM motors, and Full-Time Manual focus for around $500.
The EF 24-85mm f/3.5-4.5 USM is also a very capable lens, especially when used on a 1.6x crop factor body, which crops out the softer edges of the lens.
Start with one of these two medium zooms (the 24-85 or 28-105) and add a telephoto later when resources permit.