Would like to alter some of my button-downs to be slimm Sewing Machines Parts and Sales in Los Angeles

I’ve lost about 40lbs in the last year and now all my shirts are too big. I’ve read a bit about how to alter button-downs and it seems like it would be easy enough. I was thinking I would pick up a couple shirts from goodwill to practice on first. Do you think this is something a beginner could do (and have it look right)?