What are the other nerfs I'll need to face to achieve Level 50 as first class?
I guess you mean what's the disadvantage of not changing classes. Well, basically, any gear you find after the second dungeon can't be equipped by starter classes; you're also missing out on the skills available after changing classes.
That said, monsters aren't exactly hard to beat and you're not entirely out of options regarding gear. You can look at arby's Acolyte guide for an overview of what it's like to skip the class change.
Due to an oversight of the previous dev teams, there are a few master level items (such as cards and titles) that can be used by lower level characters, but overall you probably won't need those just to reach level 50.
Edited by faku1810, 07 November 2018 - 03:34 PM.