You are a software developer and you are using open source as your starting point and you want to know what's inside the bot?
I don't know how you become a software developer but if you are a developer you should understand what you see on the open-source and that is the inside of the trading bot.
All you need is already on the open-source except for creating your own strategies. Gekko is one of the best free ones because they already have lots of strategies and guides on how to develop your own strategy as suggested above but if you want to develop your own strategy then you can follow this guide below
- https://gekko.wizb.it/docs/strategies/creating_a_strategy.html
And the other one as mentioned above is Zenbot which is the current active free trading bot. If you want to develop your own strategy with this bot you can check the link below
- https://github.com/DeviaVir/zenbot/blob/unstable/docs/strategies/howto_create_strategy.md