Seeking first steps to reduce draw calls in mobile Unity 2D on older Android devices

[DonaldHW]

I'm a solo indie developer working on a 2D pixel art game for mobile, and I'm hitting serious performance issues during testing on older Android devices. The game runs smoothly in the Unity editor and on my modern phone, but it becomes a laggy, battery-draining mess on a mid-range device from a few years ago. I suspect my sprite batching is inefficient and I might be overusing particle effects. For developers who have tackled mobile game optimization, what are the most impactful first steps? Should I focus on reducing draw calls, optimizing texture atlases, or implementing level-of-detail systems for effects? Are there specific profiling tools within Unity or third-party options that helped you identify the real bottlenecks?