I do personally not see a necessity to have studied C before migrating from Pasal to Lua.
It might be useful to have visited Modula-2, but C is syntactically quite different to Lua, Pascal and Modula-2 is therefore avoidable effort.
Additionally, the language concept is not a dynamical one, which trains methods to solve programming tasks that are superfluous or unnecessary complex in Lua.
I know what I am talking about. And I have seen Lua code being written by C experts. Not brilliant ....
It's not that I do not like C... but it's not the most direct route to get to Lua