In normal, conversational speech (NY, USA), you wouldn't ever just 'dress'. Most likely you would 'get dressed' in the morning. Exceptions would include common phrases that use the passive tone, "dress(ed) for the occasion", or "dress(ed) for success" or "Dress(ed) up/down".
As for "change/get changed", they seem to be completely interchangeable, except that "get changed" seems to be slightly more intransitive, meaning that it can stand alone, and usually sounds more awkward when it takes an object.
For example, I wouldn't say that I'd "get changed into" something; rather I'd "change into something more comfortable..."
Another example could be this exchange of two friends, one of whom who just finished working out at the gym...
A. "I'm starving! Let's get a burger."
B. "Ooh! That sounds wonderful! [looking down] Let me get (dressed/changed), and I'll meet you here in 5."