Stellaris had several very important principles that could be a huge help when playing.
Everything served the empire's development.
All politics served the economy.
The entire economy served production.
All production served the fleet.
The entire fleet served war.
All wars served the empire.
Of course, these only worked wonders in Ironman Mode. If you just wanted to mess around or play with console commands, disregard all the rules above.
In fact, Stellaris was a very logical game. As a strategy game, it had a strong internal logic, and in what followed, I would use straightforward, easy-to-understand reasoning to guide you through a playthrough.
Let's start with the controls. To play Stellaris, you only needed a mouse, plus the space bar and M key at most.
The space bar paused the game. In single-player Stellaris, you could repeatedly pause the passage of time and carry out your actions while paused. Your hands would struggle to keep pace with the game while it was running, so pause often. Of course, you could also slow down the game speed, but that would make a playthrough drag on for a very long time.
My tutorial would teach you how to play a development-focused game, rather than going to war right away or playing multiplayer PvE or PvP. As such, this tutorial would be heavily subjective. Read it or don't; I don't give a fuck.
When you first entered the game, the sheer amount of information on the Stellaris interface would leave you stunned-the complicated UI, tiny buttons, and utterly pointless official tutorial would smack every newcomer in the face equally. So when that little tutorial robot started rambling in English, shut it down immediately (+3 minerals), then listen to me.
Once you understood Stellaris's UI and logic, you understood how to play it.