For landscapes, don’t assume the kit lens is the main problem. Technique often matters more: tripod use, aperture choice, focus accuracy, shutter speed, and avoiding camera shake all affect sharpness.

From the answers, the safest path is to keep the kit lens for now and improve technique, or test yourself with an inexpensive sharp prime like the Canon 50mm f/1.8. If your photos still aren’t sharp with that lens, the issue is probably technique rather than glass.

If you do upgrade, the Sigma 8-16mm makes sense for landscapes because it gives you a true ultra-wide option your kit lens doesn’t. A superzoom like an 18-200 or 18-250 is convenient, but these lenses are usually compromise lenses rather than the sharpest option.

Other useful suggestions from the answers:

• Rent a lens before buying if possible
• Consider the Canon EF-S 55-250mm as a strong budget-value telephoto
• A better standard zoom can make a big difference, but high-quality options cost much more

So: for landscapes on a budget, buy the ultra-wide only if you specifically want wider views; otherwise keep learning with the kit lens before replacing everything.