One thing that really helps when you use a flash, is that you can shoot with a really small aperture. I am still saving for a good flash also. In the meantime, I have made a fine little diffuser with wire, and white plastic grocery bag.
I bent the wire, which was a kind of welding rod, but you can use a coat hanger to try it. I bent it around a pipe a little smaller than the lens barrel 360º, then bent it out and up like and insect antennae, then glued the plastic bag between the wires with spray contact.
With a light squeeze of the antenna wires, it expands the loop, as i slide it onto the lens. This makes a nice soft diffuser using the on-camera flash with all of the ttl and adjustments for tweaking.
after doing the above, I found that the bottom of most images were a bit under, so I bent another wire, and use a foil faced plastic to bounce the fill for the bottom.
They nest together in the same compartment as my S5 IS, with a cleaning rag over them. It was easy to make, and works great, but I still want a flash and soft-box for other than macro.