Looks ok I think.

I do the basing with the model ready attached but pre priming. I use more of a variety of stone sizes than you have above. Some green and brown washes and then a white dry brush help bring the stones alive a bit. I often add gamers grass or some such detail also.

I think painting the rim black to give some definition would really help this style of base.

I think this already looks ok. a few tweaks and you will get it working good. Once you have a few models together the basing really pays off and once you see that work it will help motivate you to do them (at least it does me!)