Hi I'm completely inexperienced with Warhammer 40K, and I'm just planning out my first Ork army. I'm going with a Standard Missions Compulsory, Warboss and 2 troops, few other things thrown in there, 500 points. I was hoping someone might look over my tentative list and throw me some input. Thanks!

Ork 40K
1 Warboss 60 pt
2 Mek Boyz (bodygaurd) 20 pt
2 Mad Doks (bodyguard) 20 pt

7 Storm Boyz (elite) 105 pt
6 Flash Gitz (elite) 54 pt

10 Shoota Boyz (mob) 80 pt
6 Burna Boyz (mob) 54 pt

1 Big Gunz Battery 30 pt
1 Slaver/Mek 9 pt

1 Killer Kan 45 pt

I was curious whether individual Gretchen come with the Battery or have to be purchased for it, and where do I find things that aren't in the Codex, such as Wartrukks? Also, does each individual Ork need an additional weapon, or do they come armed? Thanks for your help, let me know what Im missing and what I should change