Chieftan Ballista Marauder - Advice Needed

I am not a real end game player, this league is the first time I've passed L50 on a character and I've been playing POE since 2011... I enjoyed using the Iron Commander bow so much on my ranger that I made a Marauder to take advantage of the chieftan tree (once I have run the Labyrinth.)

My current skill tree is as follows



I plan on moving up through the Scion life wheel and then on to Totemic Mastery. After that I'm unsure.

IS it worth picking up more armour nodes (Combat Stamina mainly) or moving across to the ranger side to take more bow/projectile damage oriented abilities?

Which main attack skill would you use with this build. I'm currently using Barrage, but I am considering switching to a Split Arrow/Curse on Hit but am undecided on which curse to use, I'm thinking Projectile weakness would be the biggest buff to the ballista.

I'm currently really struggling with Mana, covering that with flasks but would like a better solution so that I can actually run an aura, any suggestions regarding that would be welcome.

Any recommendations on gearing are welcome (but I don't have huge supplies of currency (never even seen an exalted, so as much as I would love a 5L Belly of the Beast it ain't happening any time soon :D)

Thanks In advance.

Absolutely loving the playstyle of this build and its the first time I've felt like even asking about this sort of stuff in order to refine it to a point where i can get to and succeed in endgame.