Both of those lenses are good, low-cost "training wheels" companions to the EF-S 18-55, and are, in fact, the lenses I got when I bought my Canon XT/350D back in 2006, but today, there are two choices that might be better.
EF 50mm f/1.8 II pros and cons
This is an amazing bargain and is easily the best value-for-price lens Canon makes, but that's partly because its pricetag is so very very low. It is an all-plastic lens, with a plastic mount bayonet, a fiddly manual focus ring, no distance scale, and iffy autofocus performance in low light. And the main reason you want it is the f/1.8 max. aperture. Compared to the 18-55 @55mm, the difference between a max. aperture of f/1.8 and f/5.6 is that you can get 3.3 stops, or 10x the amount of light from that aperture setting. That means to get the same exposure, you could use an iso setting that's 1/10th of what you'd have to use with the 18-55 kit, or a shutter speed that's 10x faster.
However, the EF 50/1.8 II is a film-era design from 1990. There are three newer choices that have a few extra things going for them:
EF 50mm f/1.8 STM — Released in 2015, this lens is a basic update to the EF 50mm f/1.8 II in every way. It has a metal barrel and mount plate, it has a much nicer manual focus ring, and includes a step motor (STM), which is good for smooth and silent autofocus. The optics are relatively similar to the 50/1.8 II's, but the overall build quality and usability are nicer, and the cost isn't much higher.
EF 40mm f/2.8 STM — Released in 2012, this "pancake" lens is very thin and discreet, and again has all metal construction. It's slower than the 50/1.8, but is closer to the "normal" field of view on a crop body, if still slightly telephoto with a 64mm equivalency. This makes it more useful as a general walkaround lens than the 50mm lens would be.
EF-S 23mm f/2.8 STM — Released in 2014, this pancake lens is designed for crop bodies, and yields a 35mm equivalency, for a wider-than-normal field of view. It's short enough to do closeup near-macros, wide enough for landscapes, but still long enough to do some portrait shooting. If you want a good street shooting or walkaround lens, this could be a good choice.
EF-S 55-250 IS
The EF 75-300 III is a very low cost lens. Its design goes back to the '80s. You can get nice sharp images out of it, but it's more limited than other lenses in that capability. You have to stop it down past f/8 for better performance. You have to keep the shutter speed above 1/300s (or higher) to mitigate camera shake blur when shooting @300mm. It's a little softer at the extreme ends of the zoom range. A lot of lenses have similar issues, but the usability of this lens can be limited.
For about $100 more, the EF-S 55-250 IS is a digital-era design, and is stabilized. Its performance wide open at 250mm is better than the 75-300 @300mm wide open, and can even rival the 70-300 IS USM (non-L)'s. The only ways in which the 75-300III beats this lens is on price, and if you also have to use the lens on a full-frame/film camera.