I'm not an experienced dropshipper (just starting as an experiment. I'm mainly a Private Label merchant and have SEO experience), but I think the niche is problematic.
How do you target your audience? You mentioned that "everybody with a phone" can be your customer. But by that information alone, you can not target them at all. How would you know what kind of case they want? There is variety starting from "simple and protective" over "Fan merchandise" to "Premium/Leather" cases that you have to target each on their own.
For example: If I am a business person that likes leather and expensive things, I am a good target for a premium leather phone case. If you set up an ad that shows me a "cool Dragonball Phone case"... well, then I will simply ignore it. And of course, the other way around: The Dragonball Fan would likely ignore the Leather Case ad.
Generally, I would pick the niche based on a topic of interest, not on a product category. The reason for it is that your shop will not likely create upsales because there is just the 1 phone case I like and the rest is just not useful to me. To use my example from above: Dragonball. If I am a Dragonball fan and your Dragonball Phone case ad gets me to your shop, I might browse the rest of your shop (if it is about Dragonball) and can find other things I like (posters, shirts, mousepads, toys etc) because I'm interested in the topic in general and not just the 1 product your ad showed me.
I would recommend doing a topic that is NOT covered by copyright (every Manga/Anime is, so avoid them. Dragonball was just an easy example). Maybe something like Dragons, Wolves, Fishing, Soccer, Golf, Gaming or whatever you can come up with. Just make sure there are several products one visitor might be interested in. Makes ad targeting and upsales a hell of a lot easier.
As for your 0 sales problem I can only come up with 3 reasons:
1. The customer does not find anything they like (casedesign or pricing)
2. There are technical difficulties that prevent a sale
3. Your shop is not trustworthy (no SSL, bad english, poor design, obvious fake timers, stupid domain name etc)
Keep in mind that Amazon is so successful because customers trust them. If your customers doubt you just one bit, they are gone.
I'm not an experienced dropshipper (just starting as an experiment. I'm mainly a Private Label merchant and have SEO experience), but I think the niche is problematic.
How do you target your audience? You mentioned that "everybody with a phone" can be your customer. But by that information alone, you can not target them at all. How would you know what kind of case they want? There is variety starting from "simple and protective" over "Fan merchandise" to "Premium/Leather" cases that you have to target each on their own.
For example: If I am a business person that likes leather and expensive things, I am a good target for a premium leather phone case. If you set up an ad that shows me a "cool Dragonball Phone case"... well, then I will simply ignore it. And of course, the other way around: The Dragonball Fan would likely ignore the Leather Case ad.
Generally, I would pick the niche based on a topic of interest, not on a product category. The reason for it is that your shop will not likely create upsales because there is just the 1 phone case I like and the rest is just not useful to me. To use my example from above: Dragonball. If I am a Dragonball fan and your Dragonball Phone case ad gets me to your shop, I might browse the rest of your shop (if it is about Dragonball) and can find other things I like (posters, shirts, mousepads, toys etc) because I'm interested in the topic in general and not just the 1 product your ad showed me.
I would recommend doing a topic that is NOT covered by copyright (every Manga/Anime is, so avoid them. Dragonball was just an easy example). Maybe something like Dragons, Wolves, Fishing, Soccer, Golf, Gaming or whatever you can come up with. Just make sure there are several products one visitor might be interested in. Makes ad targeting and upsales a hell of a lot easier.
As for your 0 sales problem I can only come up with 3 reasons:
1. The customer does not find anything they like (casedesign or pricing)
2. There are technical difficulties that prevent a sale
3. Your shop is not trustworthy (no SSL, bad english, poor design, obvious fake timers, stupid domain name etc)
Keep in mind that Amazon is so successful because customers trust them. If your customers doubt you just one bit, they are gone.