How big is your bank account? In all seriousness, you need to determine if you want to be competitive or just to enjoy the game for the Star Wars sake/ collection sake.
It is impossible for any of us to say where to start as the game has changed and evolved (some might say devolved) a lot recently. My advice is pick a faction (both dark and light) and go from there. Look into the Galactic legends and their requirements if you have an end game goal in mind.
Get yourself into a decent guild, away from the imposed starter guilds. This may take a while as a majority of guilds have a minimum requirement, and don’t aim too high or you’ll find yourself out before you even say hello.
The ingame chat is garbage, so get on discord and look up the plethora of swgoh servers and start there. A ton of resources and help.
If you’re discouraged easily, swgoh may not be the right game as the power dynamic heavily caters to those who have deep pockets, sure you can get by as free to play, but you will have those days/weeks where you feel like you’re not making any progress.
A good rule of thumb, HOARD EVERYTHING. Unless you’re actively working on a faction for a legendary/galactic legends etc, hoard hoard hoard. The gear crunch is a massive turn off for this game, even with the promised changes (get used to CGs lip service and then not doing anything)
Lastly, don’t over extend yourself trying to grind/gear too many characters at once, this goes back to hoarding. You will find you will hit a wall constantly as a vast majority of characters require a lot of the same gear and large amounts of it, and it only gets worse the higher you go into relics and newer releases.