A lot depends on your trialing situation. Are most of your trials outside or indoors? Do you typically work out of a vehicle or do you crate in the facility? Are you traveling to trials and staying in hotels? Where in the country (generally) are you?
Agree on the Ryobi fans and various other accessories (but they usually go on sale in the lead up to Father’s day so it might be worth holding off till then for that).
A good soft crate or tent is really nice to have if your dog is amenable and won’t take it hamster-balling around.
For a middle aged BC, though, a Back On Track (or similar therapeutic blanket - Weatherbeeta has one, as does Schneider’s if your dog fits their large size) might be worthwhile.
My youngster says that she cannot possibly do her best without proper post‐run treats. Currently those are minnows (and yes, I do special order them for her), but your BC may have a different opinion.