Guys get angry at the people with 100+ posts, not someone with 1 post count
He did what he could he read the guide etc.........That is 100 times better than most people here.
I don't have any personal experience with wizard but I can give you some general guidelines.
The basic fundamentals of this game is you can either deal lots of damage or take lots of damage. Not both. You have picked wizard the highest damage dealer, and the most fragile character.
This is for question #2
Now when it comes to your skills you have the same choice, do you want max damage or defensive skills. So for example the light nuke may be "weak" but it has an 80% chance of knockback. When someone gets knocked back it cancels whatever attack they were charging as well as pushing them back a few feet.
The guide basically recommends getting all the skills but if you don't have the skill experience(sp). Then I would personally focus on 1 max damage and 1 defensive.
Question3
There is no reason not to get all the skills. The right skill for the right moment as they say. Some skills will help you lvl others will help you in pvp. So focus on the ones that you like. I would say try them all. There are skills you don't need to max but I wouldn't know what they are.
Also you can be a completely different build in addition to wizard, I would recommend bard or cleric, both are helper trees, they either help you and or help others.
Though you will need lots of sp if you plan to have a full support tree. So for right now you can concentrate on just wizard.
It looks like you sort of know that to get sp you have to carry a gap.
Until you know what you are doing just carry a 4 gap.