This is my first investment property that I just purchased. Is it smart to do a complete gut or save the walls that I can save. My plan is to redo the kitchen and open up one of the walls for a larger bathroom. Some of the walls are drywall and others are plaster. Any advice will be helpful.. Thank you in advance

That is a very broad question and it can't be answered without knowing multiple things about the property. I mean it's so much to consider but we would have to know what you plan on doing with it, the property condition, the renovation costs, ARV, project scope and many other things. Buy and Hold? Flip?

The short answer is: It Depends

It depends on your budget, it depends on the neighborhood (be careful about over improving!), it depends on the results of your lead paint test (assuming its a rental), and it depends on which walls are structural vs. partitions.  I suggest that you start by reviewing area comps and consider matching what is already working in the neighborhood.

Good luck!