You said you are interested in electronics/travel/languages right? What about some of these niches:
Vacations
Printers (ink)
Cell Phones
Computer Security
Computer Memory
Laptops
Language Software
Game controllers
I think you'd need to break them down further, but my affiliate source contains merchants for those categories.
In my opinion while thinking about a niche you need to think if anyone will buy it.
For instance:
history of internet - interesting subject, but more informative than money making.
history of computer - unless you think people will purchase computers or parts by reading the history of computers, I would stay away. Not an expert, but I don't think people searching for this would be looking for parts like memory, and software (if people don't know much about computers, they wouldn't be building a computer).
history of money good - again what would you sell?
Ayways hope that helps. I had a tough time with this step as well. Sometimes you just have to think of a specific target group. For instance if you wanted to sell apparel or sports equipment. Maybe consider kids apparel or equipment, or sports equipment for the disabled.
Good luck!
You have written niches such as :
Vacations
Printers (ink)
Cell Phones
Computer Security
Computer Memory
Laptops
Language Software
Game controllers
I can sell items in here, but these niches don't have sufficient things to blog about , what do you think?
When you say sell things, do you sell on your blog/website?
How did you select your first niche?