ASK A QUESTION Is it Ok to say Mucho gracias or does it need to be muchas gracias
This is in conversational terms.
It needs to be muchas gracias. Gracias is feminine and plural so muchas must be the same.
A little harsh don't you think
No I don't think it harsh. Of course the original sense of "barbaric"/"barbarian", was "one who wore a beard". We have, however, plenty of statues to remind us that beards were not especially foreign to the Greeks (if memory serves, Zeus usually sports a beard). I suspect that then, as now, "barbarians" were most readily identified by their speech.
Dropping foreign phrases in the middle of sentences/conversations can be a sign of sophistication/internationalization when the phrases are correct/apropos but the introduction of grossly incorrect phrases is an indication of ignorance and pretentiousness.
For some reason, when I saw the original question, I thought that you meant "OK" in the "politically correct" sense and that you were talking about dropping the "mucho gracias" into the middle of a conversation in English (along the lines of Arnie's "Hasta la vista, baby!"). What I think is barbaric is the habit of some people of using (often "fractured") Spanish e.g. "much grass" or French e.g. "mercy buckup" when speaking English as an attempt at humor.
If you simply meant "Which is correct?" (which is how others have read your question), then it's not barbaric it's just a (fairly basic) error of the sort that all learners make at one time or another.
"mucho gracias" is barbaric (on a par with "no problemo").
barbaric is extreme. It is improper but that is the norm in today's society. When did disrespect become a verb? or Probably become prolly? We are just lazy as a whole and mucho is easier than muchas.
Don't let them tease you. They're really not trying to be harsh. We just get a lot of strange questions sometimes. Yours is not strange.
No, it's not proper Spanish. Adjectives have to match nouns in gender and number. It has to be muchas gracias. Don't listen to American television shows for lessons in either Spanish or English.