Budget eGPUs for Mac Mini?
You already have a 'budget' GPU inside the Mini. I would expect the Intel integrated unit to be more than capable of your workload.
There is a danger that you spend a lot of money on a GPU and not notice any performance benefit.
You can always check Activity Monitor to see if your GPU is being 'overloaded' by your work, using the GPU History panel. It's worth checking to see whether any lack of performance is caused by the GPU, or whether it's just shonky Adobe code.