Thankfully most of the grinding is menuing, so I haven't had to worry about getting tired. There are items you can use to skip playing a song but still get the rewards and event points from it, so that's how a lot of people will grind it out. Just means you have to skip the song a bunch, restore stamina, and continue skipping. Hence all the menuing.

Here's a screenshot of the rewards screen. The biggest thing is the titles, everyone in the top 50k gets a title with their placement, but anyone in the top 10 will have their exact ranking instead of just "top 300" or "top 100". Next to those are 3 different idols you can use to put in your team or things like that. For example, you can see on the left is the reward spotlight idol, this UR You Watanabe. Top 100 will get 2 of her while top 300 gets 1 (since she's a higher rarity, you have to finish higher for multiple copies). And the green gems are items you can use to raise your idols to higher levels.
The titles are the big things people always compete for, but getting multiples of the idols means you have to spend less of the green gems to bring them to max level, so it can be helpful to just get all you can.
My rank dropped from 12 to 36 in almost 48 hours, so that might give some insight into how the top rankings are. With 5 days remaining that's how I make my guess that I'll end up around Top 100 before any final push.
Hopefully that wasn't too tough or awkward of an explanation? I act like I could write a guide on this game, but a lot of the in-depth things I've just picked up from others.