What's the best strategy for spending gems in Goal Kick Simulator? Should I focus on upgrading strength, accuracy, or speed first?

Go for strength first! It's the most important stat for long-range goals. Accuracy comes second, speed is less important until you're hitting from really far distances.

Strength = distance. That's it. Max it out first if you want those crazy long shots.

I'd say balance strength and accuracy 60/40. No point having power if you can't hit the target. Speed helps with ball trajectory but upgrade it last.

Equal strength/accuracy split worked for me. Can hit 70m goals consistently now.

Strength all the way. I maxed it first and can now hit from 80+ meters easily. Accuracy is nice but you can adjust your aim manually.

Start with strength to unlock longer distances, then pump accuracy so you don't waste shots. Speed is mostly for style points and advanced techniques.