Looking through the published "British Grenadier!" scenarios, one finds the following battles as needing Indian figures:
- Hubbardton: 4;
- Oriskany: 54 (48 on the British side, 6 on the American side);
- Bennington: 8;
- Freeman's Farm: 15;
- Bemis Heights: 3;
- Indian Field: 12 Stockbridge Indians.
Delaware Indian packs for, say, those fighting for the Patriots, if you think it might get confusing on the tabletop which figures belong to which side. As for numbers, building a large force of Indians isn't difficult as there are so many different figures available in 25mm - I have Perry, Conquest and Galloping Major in my collection, but there are others available too; for example, Crusader Miniatures have some nice ones, although the poses are rather static when compared to the aforementioned. I started off basing my Indians as skirmishers on single 25mm x 25mm bases. I did think about basing new figures on larger bases in multiples, but then decided to stick with single bases for consistency. I'm minded to buy a couple of "movement trays" (something I vowed never to do) if I find myself preparing for an Oriskany game.