In my UI, I really use a handful of UIGradients. I already know that the more colors I put into it, the more performance heavy it will be, so each UI gradient only uses two colors (the minimum).
In total I have 6, but I’m really into UI gradients so I might use up to around 20. Will this become a problem for low end devices? How much is too much?
I’m no expert at the performance impact of UI, but I would guess that having multiple ui gradients will barely impact performance noticeably, if at all, since UI is rendered on the screen in 2d, not 3d. However, if you are experiencing performance issues yourself, then maybe try using less gradients if it helps. Just use your own judgement and you should be fine. Even low-end devices should be able to handle UI fairly easily.