It's a really solid arcade game with great graphics and I don't want to detract from that, but you asked for advice and I had an idea:
Instead of just building a hand, you need to reach a chip threshold, and every hand you make multiplies your banked chips.
That gives you a reason to collect chips and build better hands even if you don't care about score. And you get the extra decision-making of whether it's faster to grind chips or make a better hand.
I think it's good flavor-wise too; you play poker to win chips.