This card makes me see two things :
Something is gaining on you....
You are attempting to acheive a windfall, a monetary "gain," but perhaps being either reckless or at least unconventional in how you try to achieve this.
Man, my first thought was not $$ cha-ching, it was cha-chased! There's nothing particularly spooky about a teeny little ole horse jockey riding his race horse. But you can't see the ground. All you see is dust and clouds.
Is the rider in the lead? Or is the rider "closing the gap" in order to gain the lead?
And... horse racing and "Gain" recalls monetary gain, winnings. But there is no sign of "winning" here... no finish line, certainly no photo finish, and no trophy or winning laurel. Just the ATTEMPT to gain is shown.
Other cards in the deck clearly show the attainment of a goal, and emphasizes money itself, but this card emphasizes the process of trying to achieve the gain.
Is the querent the one on the horse, racing? Or is someone running against them?
Flight, speed, and swiftness are all implied in the charging horse, the dust clouds, and the jockey's lifted riding posture. These two competitors, horse and jockey, are still in the process of TRYING to gain. They ain't there yet....
Which leads me to one last aside : who really wins? Who really gains? Did the horse do all the work, or did the rider? Or did it take teamwork to get it to happen?
Teamwork, in general, could be implied.