Recommend a lense kit and other accessories?

I have looked at thousands of these on ebay and the net. All the ones I have seen with a magnifying lens above 2x have either a special case that the lens attaches too or the lense is fixed to a bracket & stand. There don't seem to be any variations in cases for the 8x lens.

There are fisheye , macro and 2x telephoto lenses available that can be used via a magnetic ring that is stuck around the camera. You should be able to use these with a case of your choice as long as the area around the camera has enough room for the ring to sit properly. Im not 100% sure on this but what I have read so far seems to be the case.

There are a couple of high quality custom setups available where the case looks a bit nicer but they cost like $100 or more and will only suit a particular phone.

I bought a smaller lens kit on Amazon a couple of weeks ago for my Droid Rzr Maxx, haven't tried it on my S4 yet. For $10 they work pretty well.

http://www.amazon.com/gp/product/B00F5TCA4A/ref=oh_aui_detailpage_o05_s00?ie=UTF8&psc=1

If you take a look at youtube you'll notice that most of the zoom lenses have a really noticeable blur around the edges. Some even block the edges around scope of view so the edges will be black.

The best ones I could find where made of aluminium instead of plastic. This of course increases the price but the bad lenses will only make you cry if you look at the photos or video on a big screen.

Edit: the macro and wide angle lenses seem to work well.

Edit2: Here's a review for the same lens that is being sold for S4 as well:
http://www.wpcentral.com/review-12x-telephoto-lens-nokia-lumia-920

The photos look so bad that I wouldn't buy it.