You can’t really depict how many players you’re going to get it really depends on how good of a game it looks to people. With 5k to 10k ads you would get a lot of views, but not necessarily plays.
From my experience, I had spent around 800 Robux on Ads which got me around 50 members but not a lot in the game. I would say you do sponsors and maybe start small around 400-600 and then slowly spend more from there.