Yes, the T6i would be a good camera for the money, was the first model to use the 24MP sensor, that's the same as what's used in the the more expensive Rebel T6s and 80D.
There's an valid argument for "full frame" cameras for landscape photography, instead of APS-C crop sensor such as all the Rebel series cameras. However, full frame cameras and their lenses are a lot more expensive, plus bigger and heavier.
The EF-S 18-55mm IS STM kit lens that's usually included in kit with the T6i is pretty good optically, just rather plasticky and lightly built. STM is "stepper motor" focus drive... STM is faster and quieter than "micro motor" (Canon lenses not marked STM or USM, including cheaper versions of 18-55mm and 55-250mm). USM or "ultrasonic motor" is even faster, so can be a better choice for action/sports. However, in general STM is better for video.... a little quieter and smoother. There are a few new "Nano USM" that are ideal for both action and video... but not the lenses you're considering. For more stationary subjects such as landscapes, it really won't matter. Focus speed just isn't a big concern for that or a lot of other things.
The EF-S 55-250mm IS STM is also capable of very nice images and a good value, too... especially when bought in kit where it's discounted. A telephoto such as this is most often used for sports, wildlife and similar. Not typically used for landscape (though I'd never say never). Be careful... sometimes a cheaper EF
75-300mm III (non-IS, non-USM) telezoom is instead bundled with the cameras. This is simply not one of Canon's best efforts.... the EF-S 55-250mm is a superior lens in many ways: better image quality, faster/quieter focusing, image stabilization.
For landscape photography, I'm sure I'd use the 18-55mm a lot more often than the 55-250mm.... However I know for sure I'd also want a wider lens at time. Fortunately, Canon offers one of the very best values in ultrawides.... the EF-S 10-18mm IS STM is similar build to the 18-55mm (a little plasticky) but quite capable and an excellent value. It costs around $280, where most lenses of this type are $450, $500 or more (the least expensive Nikon ultrawide is $900). Besides the price, what's really great about it is that the EF-S 10-18mm also has some of the best image quality in the category, as well as being the smallest, lightest lens of it's type... and presently the only one with image stabilization. In other words, it's a lot of lens for the money! For landscapes in particular, I'd buy the 10-18mm over the 55-250mm, if I had to choose between them.
None of the Canon lenses in this price range come with a lens hood, unfortunately. I highly recommend you buy and use those for every lens you get. A fitted, matched lens hood both protects the lens and can improve images. Canon's matching hoods for each lens cost around $25 apiece. There are also cheaper "clones" such as Vello that typically cost 33% to 50% less and probably do the job pretty similarly.
FYI:
EF-S 18-55mm STM IS lens uses EW-63C hood and 58mm filters.
EF-S 10-18mm STM IS lens uses EW-73C hood and 67mm filters.
EF-S 55-250mm STM IS lens uses ET-63 hood and 58mm filters.
Don't waste your limited funds on "UV/clear protection" filters for the lenses. Those do almost nothing... a thin piece of glass gives very little physical protection (lens hoods and caps do a much better job of protecting lenses).
Still, you may want to get some types of filters for certain purposes. Two that landscape photographers (and others) use frequently are Circular Polarizers and Neutral Density (some also use Graduated Neutral Density, but with digital those are now less necessary). C-Pol, in particular, are very useful to deepen the blue of the sky and make colors more saturated throughout a scene, as well as help reduce/control reflections. ND filters are a little more specialized, used to allow slower shutter speeds to blur water and similar in landscape shots. Of the two, I would think the C-Pol would easily be the most useful.
Don't cheap out on filters.... get only high quality glass and multi-coated, since they will be between you and your image every time the filter is used. I recommend and use B+W MRC and F-Pro Kaesemann HT C-Pols. Those cost between $60 and $70 in 67mm size, a little less in 58mm size. There are similar quality from Hoya, Marumi and others. But most manufacturers also make cheaper filters with lower quality materials and with single or no coatings on the glass. For the difference in price and because filter quality has direct impact on image quality, I would always recommend better multi-coated.
Some might suggest getting just the larger filter and using a step-ring to be able to use it on the smaller diameter lenses, too. That's okay, but be aware that you won't be able to use the lens hood when doing that (and a lens hood becomes even more important when using a filter.... especially one with multiple layers of glass such as a C-Pol). Personally I think it's well worthwhile to buy filters in the correct sizes for lenses (and have them in five or six different sizes). I do use step-rings, but only in the "filter stack" that I use to store my filters safely.
You mention looking on Amazon and that's a good place to shop. Also check out B&H Photo and Adorama in NY. Both are well-established and very reliable retailers (in fact, Adorama often sells on Amazon, I think).
You also might look at Canon's online store, where they sell "refurbished" cameras and lenses at some discount
https://shop.usa.canon.com/shop/en/catalog/eos-rebel-t6i-ef-s-18-55mm-is-stm-lens-kit-with-ef-s-55-250mm-f-4-56-is-stm-lens-refurbished). The only problem is that stock there comes and goes very quickly. I see that T6i with 18-55mm & 55-250mm is currently out of stock. Often those refurbs are demos or overstock, little difference from new... and they come with the same warranty as new. B&H and Adorama both also have refurbished and used. Might be worth a look. KEH in Atlanta is a very reliable retailer of used gear. There are some other good, reliable sellers (as well as a lot of fly-by-night, bait-and-switch online), but these will make for a good start and often have some of the best deals.
I am sure some other camera manufacturers offer similar quality and price to the T6i, 18-55 & 55-250mm "bundle". Where you'll begin to see differences are in the respective systems beyond the initial purchase. Nikon and Canon have the largest system of lenses and accessories. Third party manufacturers also make more things for Canon and Nikon, than they do for other manufacturers. However, you can put together a very capable, quality kit from any brand. Something that might help with your decision, if possible, would be to go to a store that stocks the brands and models you're considering and compare them hands-on. You might find one or another that just "feel" better to you and is more intuitive making it easier and more fun to use. Look at the ergonomics and external controls, as well as the features that are most relevant to the type of photography you want to do. Also compare the menus, how well organized and useful you find them. Some people have preferences for one brand or another. I use Canon gear and that's what I know best, so it's what I focused upon in my response.
I do agree with some previous responses, that there isn't really all that great a difference between 15 or 16MP, 18MP, 20 or 24MP. Unless you make really big prints (larger than 13x19"), you won't see much difference.
Among Canon APS-C models, the 24MP sensor is the "latest and greatest"... with slightly wider dynamic range and that extra little bit of resolution. The 7D Mark II that I use are a one generation older 20MP sensor and work just fine and are a better choice for me because I shoot more sports/action/wildlife with my APS-C cameras, and use a full frame camera for landscapes, scenics, cityscapes, and architecture. But I've made my share of landscape shots that I'm quite happy with using 18MP, 15MP and even lower resolution cameras.
On the one hand, it may make sense to get the "latest, greatest and best"... but on the other hand, it might be a worthwhile trade-off if buying a Rebel T5i kit instead (18MP and a simpler 9-point autofocus system) leaves some monies for some other things (an ultrawide lens, extra memory cards and batteries, filters, post-processing software such as Adobe Elements 15, extra hard drive storage for images, a good solid tripod, etc., etc., etc.) Only you can say, which is the better choice for you.
Hope this helps!