Now what

I win 200 floors. Now, what should I do???

buy a map in the shop or kill a cartographer and carry on… try to reach level 350 for example ))

500 or bust. If you do not want a guaranteed lv100 eternal then yeah stick to something lower than 500.

I don’t believe there’s a max lvl dungeon, so after 200 find the Cartographer on each map from 200 on. He drops a map for the next floor. I’ve read someone is floor 1700! I wonder what floor on very easy is par with mythic 3 floor 200?
Now it’s all about finding Uber gear and tuning your gear to millions or billions of dps. Search for crafting strategies and read up on affix caps in forums. Be prepared to farm crystals and mythstones. This game is about the long grind, which is one reason I love it.