Hey SaHaRzZz,
So you are on the right track to in regards to getting the tiling to look less apparent, however; your rock texture and gravel textures do not seem to be very good for tiling. A tileable texture is going to have less noticeable edges when placed on a surface repeating as the edges match up with one another.
To help hide your edges you can follow a number of routes, each with their own caveat and performance impacts. Have found the most effective way to hide tiling is to multiply the same texture at different scales on top of one another. We do this with some of our Starter Content, and it is called Macro Texture Variation. Below is an example of how this works and how to implement this within your own material.
Macro Variation
Without Macro Variation
Above you can clearly see the texture tiling and repeating, which is the same problem you are having. Once you connect your Base Color texture samples with the macro-tiling variation, it will be hard to spot the repetition.
With Macro Variation
As you can see, the tiling is nearly impossible to spot when you use this approach. There are other ways to get the same effect but could prove to be more costly. Since you are using the same texture for the macro effect, you are not consuming multiple texture samples. Let me know if you have additional questions.
Cheers,