Don’t worry that much about making mistakes.
While i can understand, that people sometimes have fear to make mistakes, it’s part of the learning process.
LE is much more forgiving than PoE.
Literally the only thing that you are permanently bound to, is the mastery choice, after Chapter 3.
So just put some thought into what mastery you want to play.
In case you wanna play a different mastery at some point, you need to play a new character.
Of course there are plenty of little tips and trciks that can make your life easier, but it’s just those will becoem clear to you over time anyway.
Also i would highly advice you do not follow a build guide, since you can literally make everythign in LE viable.
Of course your first build might be not as good as some of the really thought out builds, but you will be able to “fix your own build” relatively easy, once you get a better understanding of the game’s mechanics.
If you really feel unprepared i can suggest Wast3d’s LB Mage Guide
You don’t need to follow the build guide itself, but there are alot of general tips for crafting etc. in it, if you read through it.