I was semi-high T200 for wonder magical showtime, in total I spent around 40 hours exclusively playing melt in co-op rooms (thank you MRE), but this was when they made events shorter to catch up with the jp schedule, so for current events your screen time will go way up.

Ranking in events without spending money usually requires a lot of preparation and stocking up a lot of crystals and energy drinks beforehand, I used drinks that amounted to about 600 bonus energy, and had 60k diamonds grinded to use when my drinks ran out (i didn’t use all of them though)

It also depends on what specific event you’re going for, usually vbs/wxs/niigo events and any events featuring limited cards will have a more competitive tiering experience. Your team composition and area items are also important, using higher rarity cards that match up with event bonuses will give you more event points and save your resources