Try sell the most popular things in the world, thr indemand thigs, Like cellphone.You can have a great profit in it. But if you sell make sure that it is lesser than the mall price, The cheaper the more customer comes.
I would to add something from this when you are able to sell all of this. You must think about what the trend is, and I would like to say that we are in modern technology days and people are dwelling more with their smartphones (Androids & IOS) so if you are going to build your own online shop make sure that it supports those platforms.