Before you go out and spend a heap of time & money....
How does the bike climb hills as it is?
What are you lacking?

34x25 or 34x28 gearing should get many riders up a lot of moderate hills.

What is your weight? Are you carrying cargo?

An option might be to go out and practice climbing hills with your current setup, and you might find that you don't need some fancy custom configuration after putting in a little work.