How to improve accuracy in general?

[danielweipinglee]

The input data seems pretty straightforward, in my case, I have date, revenue by date with each media channel spent, data size is 180 (days), however, when I run the model fit, the R2 never goes beyond 0.5 and the MAPE is always around 30%. I have tried to adjust the amount of warm up, samples, etc. But still couldn't get better results.

Any tips or recommendations would be highly appreciated, and if more info is needed, please let me know as well, happy to clarify!