Try sword dance first since its probably the strongest option right now, works great with keen affinity and lets you close gaps fast while dealing serious damage. Good to know you can chain attacks together and itll only cost 6 fp per swing, perfect for aggressive playstyles. Unsheathe is solid early game especially on katanas but youll want to swap it once you get better options. Storm blade got buffed recently and works surprisingly well now, gives you good ranged options when enemies start running away. Double slash is worth checking out if youre running any status effects, works really nice with bloodflame blade to stack bleed quickly. Just remember some skills need specific weapons to work properly, and make sure to upgrade your weapon since most skills scale with that anyway. Interesting bit - switching to keen affinity makes these work even better with dex builds but dont forget about the fp costs when planning your setup.

Thats pretty much everything you need to know to start destroying with dex builds just practice the timing a bit and youll be fine.