For a first time don’t try to get the strongest character possible. It’s a time sink to do that. Usually the main campaign of games are beatable even if you screw up something. The worst that can happen is you backtracking a bit and spending time to level up before doing the next quest.
When you played the game once and got used to the mechanics you can make a 2nd char and plan it more deeply ahead if you wish. You know what mechanics you like so the prospect of finding what to invest in what is worth etc… becomes more streamlined. But you don’t have to. You can just be happy to have finished the game and call it a day.
That’s what I did for Diablo 4. After the main campaign I did not feel like venturing more into the game or making another character so I started playing another game. If you really want to 100% a game it does require a ton of time and planning but you don’t have to