Comma before "and" which is being used after a list of items containing other and/s

I am confused about whether one should put a comma before an "and" which is being used after a list of items containing at least one other "and".

I don't use the Oxford comma, and I feel it's not necessary to put a comma before an "and" which is before the last item. I do know that if one item has an "and" in it, then we have to put a comma before the "and" to clear any ambiguity. But I am confused about a particular sentence which is mentioned below:

I will certainly go to university with a more motivated and mature attitude and contribute to its multicultural environment.

Here, I don't think a comma is necessary before the "and" which is before "contribute", as there is no ambiguity. So should I put a comma or not? If I do not put one, is it grammatically incorrect?