Suggested Charms: I looked over Darla's and Josh's character sheets, since neither of them have access to the book. I came up with some suggestions for each character. They are only suggestions. Indented charms require the charms above them in order t take, in addition to other requirements.
Darla's Suggested Charms: Archery. Presence, and Ride charms seem like the best options. I'd also recommend dots in Artifact (for a artifact rifle) and/or the Familiar background (for a superb horse)
Essence Arrow Attack (Archery 2, Essence 2, 2m): shot does extra damage and chosen effect
Phantom Arrow Technique (Archery 3, Essence 2; 1m per arrow): creates one arrow (only)
Inexhaustible Bolts of Solar Fire (Archery 5, E 4; 7m, 1wp): infinite ammo for one scene
Inexhaustible Bolts of Solar Fire is absolutely necessary for your character, but you can't have it

. It lasts for a whole scene, and, unlike Phantom Arrow Technique, grants ammunition of any type, including firedust. Unfortunately, it requires Essence 4.
Any Archery Excellency: bonus dice or successes
Trance of Unhesitating Speed (Archery 3, Essence 2, 4m per shot) Flurry without accuracy penalty and only -1 DV, free reloads, max attacks = Essence +1
Arrow Storm Technique (Archery 5, Essence 2, 8m, 1wp) Single attack hits E*3 targets
Trance of Unhesitating Speed is definitely worth getting; it's cheap to use and only requires one Charm. Arrow Storm Technique is less important, though very nice.
Any Archery Excellency: bonus dice or successes
There is no Wind (Archery 4, Essence 1, 3m) Negate all external penalties for a single attack
Accuracy Without Distance (Archery 5, Essence 3, 1m, 1wp) Perfect Attack. 'nuff said.
Accuracy Without Distance is a Perfect Attack, which means that it always hits – if the accuracy roll is less than the target's DV, the attack hits anyway, but receives no bonus damage dice from accuracy. The only way to stop a Perfect Attack is with a Perfect Defense (see Josh's Dodge Charm list).
Any Presence Excellency: bonus dice or successes
Hypnotic Tongue Technique (Presence 3, Essence 2, 10m, 1wp) Command a target
Irresistible Salesmen Spirit (Presence 4, Essence 2, 3m) double successes on influence roll
One of these is a command (Mind Trick, Dominate Person, etc), and the other augments an otherwise normal persuasion attempt. I wouldn't recommend both, but one would make sense.
Any Ride Excellency: bonus dice or successes
Worthy Mount Technique (Ride 3, Essence 3, no cost (constant)) charms used to help self can also help mount for the cost of one additional mote.
This charm would be very useful to a melee-based rider, who could use various Parrying charms to defend his mount, and various Athletics and Survival charms to improve the mount's abilities. It is not as useful for your character because you need to have these abilities to use them on your mount, but it could come in handy.
Any Ride Excellency: bonus dice or successes
Flashing Thunderbolt Steed (Ride 5, Essence 3, 10m, 1wp) Touched mount moves Sta*10 mph
Flashing Thunderbolt Steed lasts for one day and gives one automatic success for all checks to avoid obstacles and the like. It also allows the horse to run at its Stamina * 10 miles per hour (standard horses have stamina of 3). Best of all, it applies to any single mount you touch

. The only drawback is the charm costs one willpower, so getting the whole circle of six people going would be somewhat draining.