Most shader packs you find are either so advanced they require a top of the line machine to play Minecraft, or they are so basic they don’t really do much to change the appearance of the in-game world. Once in a while, you see something like the KUDA Shaders mod, which is specifically designed to work with increased settings on newer computers, but still works on older, slower computers at the same time. Because you can adjust the effect levels and change the amount of strain being put on your computer, this shader pack really stands out from all the other shaders available.
Download link: KUDA Shaders Mod 1.8/1.7