I pretty much just beat this game. Unlocked all scenes, have 19/23 decorations, and can finish each new level in ~5 minutes often faster (current level 48). So here are some tips:

1. For all intents and purposes, the game ends at stage 20. The girl-level requirement to reach the next stage caps out at 5000. Once you can hit that number use your time boosts to farm a few stages worth of stock and up the girl-multiplier decorations. Eventually the process of grinding a stage is super quick (5 minutes or less), and maxing everything is a question of how long your willing to grind stock.

2. Auto-clickers are a must for this game. It's no fun breaking your hand farming keys on private shows.

3. From the above point, spend your first 3 skill points on the active-player route to get the all-private-show-clicker, then spend your next 3 skill points in the inactive-player route to unlock the mega-coin. After that max active-player route before putting any more points into the inactive route.

4. The only girl that matters is the 11th girl (once you get that far). Make sure that the 11th girl is your girl with the highest multiplier, as she produces (by far) the most cash for the amount you spend on her. If you ever have the option to spend money on two different girls, always choose the highest numbered one.

5. You can actually aim for the multipliers on the daily wheel spin. It's definitely more of an art than a science, but you can raise your chances of landing on the multiplier bonuses, and those are by far the best things on the wheel.

6. Stock Market is a god-send for players in stages 12 - 20, as you often will get caught with just 200-400 girl-levels left to finish the stage, but each of those levels being way to expensive for your current income. Stock market gives you an easy way to continuously double the money you have saved up.

And yes, this game is buggy as hell, so if you are looking to start playing it, know that going in.