GeorgeK got his on ebay for a buck. Of course it fell apart. Haha.
Any of the $15-30 Amazon ones are fine. Most are returnable. I've ordered two in the past, all work fine. Most are made of an aluminum frame around the lens, and the clip is plastic. When you are shooting macro at close distances, forget about autofocus. It's completely useless. You will focus by gently shifting the camera back and forth. I use an iPhone and an app called PROCAMERA that allows the user to adjust everything manually, like the focus point to ISO to shutter speed. I'm a working photographer, so knowing these things helps.
And worth mentioning again, it is very very important to properly light your subject. The closer your camera gets to the subject, the harder it is to get frontal light. The higher magnifcation lenses (20x and above) will have high distortion and reduce your depth of field and require the camera to be much closer to be in focus, so lots of things will be blurred out and only a small portion will be in focus. 12x to 15x is optimal, depending on the focal length of your camera phone.
While the macro clipons are great, there is still a learning curve, and if you read many of the reviews on Amazon, a lot of the users do not realize this and give the lens a bad review, blaming the hardware instead of user error.
I mostly want the entire apparatus to be good quality. As in, actually stays clipped on, actually fits over my phone, ideally with it's case still on, etc. Doesn't fall apart, like what happened to GeorgeK. My phone is a Moto G4 with a 13MP camera. Pictures come out good when the auto focus and stability turns out well, but it's not great. I'm used to my Olympus for taking serious photos, but a lens for that would range in the hundreds of dollars. Although I would probably use it to take a lot more pictures than just pictures of ants, it's not an investment I can really make just for a new hobby.