I have actually been selling online for years. And I started with $50 facebook ad credit I got through GoDaddy. My advice would be to use a niche that has a decent following, but isn't completely saturated. For example, right now I would not try and sale anything related to Pokemon like the OP has listed. Since the release of Pokemon GO, the ads related to Pokemon are EVERYWHERE, and so the ad is gonna cost more to compete with everyone that is also selling Pokemon products. I recently started over from scratch and did everything the OP said to the T, except I used a niche that was not saturated (I used a knitting niche, LOL) I went to Audience insights on ads manager, I searched knitting. I used that info I found and put it into my ads manager when I created my first ad. I used the main "knitting" interest, I used a facebook page that was related to knitting, and I used a couple other of the "suggested" interests. I added the age demographic, which was older (40-65+), and used ONLY female demographic, and only in the US. I found a knitting kit on Aliexpress for $3.49, and ePacket shipping which was $5.37 total for the product and the faster shipping (faster delivery times = repeat customers). I then created an adset of a picture of the product which was 2000x2000 sized. When I created the ad I used terms like "Limited holiday sale" etc., and I set the price at $15.99 with FREE Shipping (rather than free+shipping) I set my ad to $7.50 ($52.20 per 7 days) , website conversions: ATC, and I set it for 7 day conversions . The first day I had 2 sales ($21.24 profit). Over the next 6 days I ended up getting another 17 sales ($180.54 profit) which payed for my ads with around $120 left. I continued the ads and right now I'm averaging around 10 sales a day, it's been running since the day after OP posted this tutorial.
I know that's a long ass message, I just wanted to list the changes of the method I used, and wanted to show you that even small niches with a low following can make you some killer money! Hope it gave you some ideas or some insight about trying this method. Good Luck!