gimme a tl;dr version, because playing up to lvl 13 didn't gave me a clue about skills
is there anything i should avoid, or save skills for later?
honestly i didn't get the system at all

On the d3 site there's a skill calculator. It'll tell you whatever you need to know

you dont spend any points, you get everything and can change what you choose whenever you want

i thought it worked this way, but wasn't sure

awesome, this way you can try out any build without replaying char thousand times

yea like 10 sec cooldown after you switch.

I will be making alot of macros to change builds quickly most likely