The best gear for a rando race is . . . rando race gear!
The specialty etailer Skimo Co has many helpful articles on race gear along with comparison charts for race skis, boots, and bindings, plus "near-race" lightweight skis, boots, and bindings, and other gear too.
For expert fitting and modification of ski boots, Green Mountain Orthotics Lab has extensive experience with many of our rando race boots.
(Plus a location at the base of our race venue Bromley allows you to test any boot mods by skinning almost literally out the door! And the Stratton location is only a several-minute drive from that uphill-friendly resort.)
Even if you don't want to go all-out on race-specific gear, a race-specific ski pack allows you to attach & remove your skis for bootpack segments without taking your pack on & off.
(And these packs are great for shorter ski tours plus off-season hiking, biking, etc.)
You must wear a helmet at all times during the race, and that helmet must be certified for either skiing or climbing (or both).
For those too modest to appear in public wearing a one-piece lycra race suit (women-specific models too), a race top/jacket combined with any reasonable soft shell pant/tight (women's here & here) offers almost all the same benefits as a full suit (especially climbing skin stowage).
Plus check out the gear swaps at Utah Skimo, Facebook, and right here.
Finally, although you can't buy fitness, you can buy skimo-specific training manuals.
(For training venues, resort uphilling policies are available at USSMA.)