What you're looking for are probably two different lenses, particularly if your budget is limited. When selecting any lens, you need to consider the following factors:
- What you need it for; this can help you determine the focal length and max. apertures you want.
- How much you can spend; this will put a hard limit on the focal lengths and max. apertures you can get. Also whether or not professional "L" lenses are in the mix (i.e., if you have less than $1k to spend, they're not)
- Any additional special features you may want: stabilization, focus motor type, macro capability, focus limit switches, etc.
- Your willingness to go for older, used, and discontinued versions of a lens.
- Your willingness to purchase 3rd party lenses.
... since the focal length of the kit lens is small, I couldn't take
pictures of objects which are far away.
You could always get closer to your subjects. But what you probably want here is a telephoto lens (> 50mm focal length equivalence, and probably closer to 200mm or 300mm), probably a zoom. The typical budget recommendation here would be an EF-S 55-250 IS STM, but there are several options you can look at, depending on what you want to shoot and your budget. See:
In portrait photography, the background is not that blurry. I believe a lens with better focal length can resolve these issues.
There are actually multiple factors that come into play when it comes to getting a thinner depth of field and blurring a background:
- The subject distance (i.e., it's why you can blur backgrounds with macro shots even with a phone camera). The closer you are, the thinner the depth of field gets.
- Subject-to-background distance (the farther away they are from each other, the easier it is to get blur, but a background that's only inches away may be difficult to blur at all)
- Aperture setting the bigger the aperture (smaller the f-number), the thinner the depth of field becomes.
- Focal length of the lens (the longer the lens, the thinner the DoF becomes)
Focal length might help, but might be counter-productive, forcing you to be farther away from your subject than you want to get enough background blur to make you happy. Max. aperture may be the easiest thing to purchase a lens for if you want to blur backgrounds. The most common recommendation here will be to get a fast prime (non zooming lens with a max aperture of f/2.8 or faster). An EF 50mm f/1.8 STM, but you could also consider the EF-S 24mm f/2.8 STM or one of the f/1.4 and faster lenses, which are more expensive.
Getting something like an EF 85mm f/1.8 USM or EF 100mm f/2 USM would probably get you even more background blur than a 50/1.8, but might be too narrow on a crop body to do more than headshots at a comfortable working distance.