I was thinking maybe a coffee filter would work, but then it might not have enough time to fully brew the ginger. I don't know what other ways to filter are good. The powder is very fine-grained, and dried ginger is really expensive right now.
I think, even though it’s way subjective, the best way to make ginger tea/(infusion actually) is to boil the fresh ginger in hot water for 4-5 minutes, and discard the ginger.
So modifying this recipe, and adapting for ginger powder, you should boil the ginger powder for some time and then filter using a coffee filter. However you should try to find the optimum time here, I think it will be less than the time needed for fresh ginger, as the powdered ginger will have waaay more surface area than the fresh ginger.
I drink ginger tea (from bought ground ginger) with honey and lemon to soothe a sore throat and for that I just drink it slowly leaving the ginger in the bottom of the cup. That's the low tech method but certainly possible. It seems to clump a little, but I don't know if the honey and lemon affect that.
If I wanted something better I'd use two mugs and steep the ginger in water in one, for a few minutes, then pass through a coffee filter into the other (no need to boil the ginger in the water). A one-cup filter cone would seem ideal. I'd certainly make the effort to do this if I was making it for someone else.
Your best bet is probably disposable empty tea bags, since they would allow you to submerge the powder in hot water yet keep it contained. They can usually be bought in bulk for fairly cheap (100 for under $5 USD in my area). Since they are usually meant for loose-leaf tea, you might want to double-bag them (with the inside one upside down) so that the opening is better sealed.