How do I portray a character in a play with my beliefs and philosophy,

[Olivia]

but as a different person? I need to make a character to represent myself, but not be me.
Tips and pointers would be helpful! Thanks!

[King_Duck]

A mouse would be good.

[will_o_the_west]

Are you writing or acting? If writing, then do the first draft with the real you as that character. Then as you revise it you can change the character's age or gender or ethnicity, changing the first draft and adding new material to reflect that.
As an actor, you'd depend on make-up and disguise, and really practise "being" the different person.