New player- Surviving hardcore with a wand marauder (+ lengthy story!)

Hi everyone. I've been playing the open beta for about a month. My gaming history is mostly MMO's and this is my first click to move/all ur camera angle r belong to us game.

As a former MMO number cruncher I'd like to think that I'm coming into this with a sort of innate understanding of the fundamental mechanics, so I won't need to be spoken to like a complete child, but that being said...

The Marauder seems like it gets access to the most off-the-bat life and resistance nodes in the passive tree. I rolled a hardcore witch first, cleared the first zone and then gave the dropped skills to my stash for the Marauder to use.

I wanted to go with the wand on the Marauder for the initial survivability from the class/tree positioning paired with the advantage of kiting/ranged DPS, so I rolled the character I'm actually playing after having secured some skills for him.

My main attack has been fireball. Damage output has been low since my upgrade options wand-wise are limited- it's proven challenging at this point in my career (level 17) to build enough INT for ideal wand upgrades and continue to point my skill tree towards life and res nodes.

I've also been having mana issues as I'm running Anger in an attempt to sort of supplement my damage.

I feel like I can tackle the mana issue down the road, but I'm hoping to do so without dying. Once I can collect more HP and regen nodes I'm thinking of picking up blood magic.... But I'm worried that I'll just kind of doom myself.

Anyways. Any pointers would be appreciated- I mapped out a pretty general build of forethought and what I've done so far combined. Link is here. Any pointers would be appreciated.

http://www.pathofexile.com/passive-skill-tree/AAAAAgEBxthYY1BQjM_2SF8_VEnnUu8Oud3yL2o7IPBE5xznqBhqHtlhVw3SISUnXUlnm64-d-OezVW1wQR5aAtheA3QR6bPGtlYrzboOlLfv0ZpZKMaVWEhhO907XrvYEsFLcRYJ9U8Lcau_gryRedjtz56uK6Tplc64YjxtfJuqjJ-QYeCxyj6lSAquuvuuJPN-nyDYqyhbdadES0=

I also had a few questions about skills- I'm currently using fireball as my main attack, and I've seen the pierce/increased projectile skills in videos making it much better. Most importantly, what would be the quickest way to pick those skills up, and getting linked gear to fit them all in?

Also- why are some of my skills 'unable to be leveled'? Is this because of stat discrepancies, level discrepancies or none of the above?

As a final afterthought, I feel like I'll be aiming towards more of a fire casting wand Marauder build. Is this even doable on hardcore, or is it a pipe-dream for unforeseen reasons?

Oh and I forgot- for the 'Iron Grip' skill. Does 'projectile attacks' mean that all wand damage regardless of type (ie; in my case, fire) will be enhanced by strength?
Thanks for reading!

I will try to comment on paragraphs in order you wrote them.

For spells the only relevant stats on wands are Spell Damage % and Cast Speed, to simplify. You do not need to upgrade to a higher level wand unless it has those kinds of stats higher. The innate physical damage of the wand and any possible elemental damage additions do not add up to spells.

Mana issues; you should've taken Clarity from The Caged Brute quest with the witch. It's an aura which provides mana regeneration. It is also enhanced by Mana Regeneration % bonuses; so pick some of those up (Paua Amulet type of stuff).

Anger is an aura which provides elemental damage (fire type) but it only works on Attacks, not Spells. (hover over any gem in the game; a tooltip appears - at the top you can see for example "Spell, Projectile, AoE" - that means it is only enhanced by things that enhance those attributes, to simplify)

Blood Magic is not quite the best option for a spellcaster marauder. Read above.

Now, Fireball is not quite the best option to go for, for several reasons, but lets not make this too long. Check into Freezing Pulse, Ice Nova, Firestorm... My honest recommendation would be Freezing Pulse (much better damage output than Fireball, and it provides CC in form of Chill/Freeze ailment on monsters). Going for fire damage is not really a pipe dream; however you will need to make quite some research around, as Fire is considered the weakest of the three elements, and requires some special building to work.

Iron Grip won't affect Spells (read above about Anger). Instead you get to use Iron Will support gem, which transforms all the STR damage % bonus into spell damage %.

And lastly I will not recommend you any passive tree build just yet; I would rather see your response first and know you are a bit more familiar with what's going on. The best approach would be to just play with your original build and see where you hit a brick wall, then remake the character with a fix to it. That can be rather time consuming to do up to endgame; so rather use the opportunity to get more familiar with the game mechanics, and then with the help on forums craft a working build.

EDIT: PoE Wiki