What is the best gpu to invest in for etherium mining ?
Nothing!Look around and read a few crypto news, so you will understand why the answer to your direct question was "Nothing."
So, did you have some other plan, which coin (Algorithm) that interest you more besides the one that you mentioned above?
Seem like you were new on mining, right? You could read more about mining (basic knowledge), then you can move to technical topics and so on. Then you can start to build your first rig, and earn more experience in every process, (and of course some profit
)