Let me start by saying I'm writing this off of my own memory. The unrouted Tidal Medal goes for Zaleo with the daily UMV. That could kill a run if you get incredibly bad luck. The Zaleo always starts at level 15. Then in the run he grinds Ray until level 30 for 19 minutes, then progresses the story before grinding until level 40 for 28 minutes, then using powerfruit till level 50.

If I recall correctly there's a guaranteed Slugling spawn in one of the houses in the mushroom village (I don't remember the name) early on. This would allow it to level up when grinding the starter thus saving a bit of time. However, Gastroak is so much slower than all the theatre loomians, which should be fine until Deludrix comes into the mix. That guy is faster and got Pheroblast, even with an 8 level difference I'm not sure if Gastroak could tank that.

I don't know though, the guaranteed Slugling house might not even be real