MTG Salvation

I've been recently digging through my cardbox, came across a copy of Brion Stoutarm I got a while back, and after looking it over, I'm thinking of building a Giant Tribal deck that focuses on flinging his fellow giants. While I have a good portion of the deck already gathered together, I was hoping I could get some recommendations for the following cards:

-Pumping: Namely +X/+0 cards so that I can pump my creatures as high as possible before being sacrificed, or generic tribal cards that help increase the power of a selected creature type.
-Threaten Cards: Namely cards that steal my opponent's cards so I can sac them instead of my own.
-Untap Effects: This is the main type of card I'm looking for, so that way I can keep tapping/untapping Brion for massive fling damage.

Any recommendations will be greatly appreciated!

Unwilling Recruit checks two boxes!

Is manifest a good effect for this? String of consciousness here: These colors are bad at CA. Something like Mastery of the Unseen gets bodies out. You can blink them into giants or sac then recur (given white’s ability to do that).

Well for tribal giants can't help. But if you threw in some dragons with firebreathing you can pump before flinging.

Ummm...if you're saccing a bunch of your dudes...Reinforcements?

Thornbite Staff is all you need. There's a lot of white tutors for it, too. Sunforger is also excellent in this deck for a toolbox package and it gives anything +4 power.

Shared Animosity and Crescendo of War pump power. Sword of the Paruns also does this, it's an equipment, and provides an untap effect.