cash only. not gifts
I have never tipped a outfitter(you pay them for the hunt)
Tip the guide. and that greatly depends on the quality of your hunt, the cost of your hunt, and how well the guide worked for you and listened to you.
USD is the currency to tip in, doesn't matter where in the world you hunt.
Tipped or fly fishing guide $100 per day,
Tipped my PH in Africa $500 each(two of us on the hunt)
I am not a rich guy, so I think it depends on your funds as well.
10% is a good starting point for a tip for a guide.
But don't feel obligated to tip if the service sucks, I have had friends that hunted big bears in Alaska, and the guides were totally useless, and the outfitter pulled them off a real good spot to put one of his "good clients" on and they then shot a huge bear that afternoon.
They did not tip at all.