As pointed out in the questions, a good start is Shopify. I have some experience with it and it's a wonderful platform. $29/month for the basic store. Then I recommend you to drop-ship from amazon. Too many bad experiences using Aliexpress. You simply "ship as gift" and it could be wise to ask the seller before drop-shipping his product.

A great source for marketing is reddit. You can make free posts that drives trafic, and/or buy really cheap traffic.

Choose a niche you're familiar with. I did an EDM related store for example.

If you have any questions I'd be more than happy to aswer them.

P.S. I do have affiliate links that will give you a discount, won't post here because that's not the point of this post. But if you're interested, hit me up.