Site to make investment(s)


I’m new to Drupal, been reading some books, going through different tutorials and trying bit of this and that. Still a bit overwhelmed by its complexity.. 😀

My first project is a site, where user is able to buy/sell monetary investment(s) of different sizes after authentication and monitor monthly paid profits of his/her investment(s). I’m going with D7 (mainly) because the authentication module is not yet available in D8.

Admin must be able to monitor all users & their investments and add profits to investments after they’ve been paid in real world. No need for automated calculation and/or payment of the profits at the moment.

So user can browse through his investments/profits in his account page and edit his contact details.

I’m a bit confused where to start. Drupal Commerce has modules for the payment methods needed, can or should I use it?
Where should I store user information/investments/profits? Should I make custom DB schemas in a custom module or something else? Total newbie with this.. 🙂

Any help appreciated.

Drupal version: