I'm guessing but what may be confusing is that a lot of skills start as magicka skills and then morph into either an allegedy (but now always) better magicka skill version or into a stamina skill. If so you unlock the magicka one then later morph it to stamina.

So for a bunch of the skills you start magicka and then take the stamina morph. This works in practice because although the game still implies you are gaining health/magicka whatever what actually is happening because of the difficulty scaling is that you are merely becoming more specialized. Thus a low level toon has plenty of magicka even without points in it.

The second reason you have some magicka skills is that even at CP 160 with no points in magicka you have a fairly reasonable base magicka and recovery (even more so for some races) and you want to be able to use that too. Thus having some magicka skills lets you draw on that smaller pool for long duration low cost or rarely used skills.

For the dual wield, just wield any pair of one handed weapons and go brutalize a chicken or squirrel. That's enough to unlock the skill line. You can level it pretty fast either by having it equipped in a dungeon or via questing. Unlock dual wield, get and slot the first skill skill from the skill tree and do a random normal dungeon. If you also read an XP scroll or use the festival XP boost you can go in on level 10 and come out of the dungeon about level 15 and you'll have made a decent progress on the skill line. If you also do a battlegrounds on the same double XP boost you'll be well away (you only have to be in a team that comes 1st or 2nd so if you do 2 or 3 you'll end up getting the XP bonus no matter how bad you are).

Useful hack: experience boosts the skills you have slotted on the front bar at the time of award plus weapon wielded and armour types worn. That means you can do a big quest line, slot the skills you want to boost, walk up to the final quest hand in, hand the quest in and then switch skills back.

I always start a new character by killing wildlife with each weapon type just to unlock the skill lines, then wear 3 of each type of armour and take them back off to get the armour lines.

You don't have to be dual wield anyway. There are advantages to both 2H and dual wield options and you'll find builds of both.