How to make a language sound different from the proto lang?

So, I'm creating a semi-naturalistic language and I have already made the proto language, and now I want to evolve it and make it sound quite different from the original, and I'm not really sure how.

My proto-lang is made up of purely CV syllables and stress on the second-to-last syllable, so for example I have words like takaru.
I could make a sound change where the vowels in the syllable preceding the stressed one dissapear, so it would be tkaru.

And now what? There are a lot of words like this in my language, and I can't figure out what sound changes to apply to make it evolve nicely. If you could provide some advice I would be grateful.