I'm an American who's married to a northern Italian, so my primary reason for learning Italian is to be able to communicate with his friends+family (who don't speak English).
For those who don't know, each region (and each city within each region) in Italy has it's own "dialetto" which is a completely separate language and can't be understand by people from other regions. For example, if my husband hears a dialetto from a city that's 2 hours away, they might as well be speaking Greek as far as he's concerned.
In addition to Italian, my husband speaks Bresciano (his area's dialetto). It's very common for people to include dialetto words when they're speaking Italian amongst themselves, or an Italian-Bresciano version of "Spanglish". In addition, there are vocabulary words, expressions, verbs, and slang that are Italian but are only used in certain regions.
Knowing all this, at first learning Italian felt like an impossible task. I decided to try to keep things simple for myself and keep my goal in sight; I wanted to communicate with northerners (though he does have one very close friend from down south, which complicates things a bit
So I started watching youtube videos of only northern Italians. At this early stage, I found standard Italian to be difficult to understand because I was only used to the way Brescians spoke. As an aside, Bresciano is considered to be the most vulgar and low-brow of all the dialetti, which is something that I happen to love!
Eventually, as my comprehension improved, I started to watch more "standard Italian" things like TV shows. After a few months of that, I started doing conversation exchanges with two southerners; I was terrified at first that I wouldn't understand them at all (southerners tend to overuse the remote past verb tense while in northern Italy it is almost never used, for example.) However, I realized that my fears were unfounded because I have no trouble understanding either person, and speaking to these southerners has given me the confidence that I can talk to anyone in the country, not just northerners.
Since in my situation I have a reason to focus on one particular regional variation of Italian, I don't try to remember or use other regions' specific vocab, but if I come across an Italian word used in Brescia (for example: pota) I do try to use it when talking with my husband's family though I never use them with Italians from other regions.
My personal take is that it is unnatural to use the accents, slang, vocab, expressions from all regions. I'm an American, so I speak American English. I watch enough British TV shows that I'm very familiar with their slang and weird ways of saying certain things, but if I were talking to a Brit, I wouldn't suddenly start trying to speak as if I were British, so it doesn't make sense to do this in a foreign language, either.
I think it makes sense to pick one that you have some kind of connection with and try to emulated that accent, while still being able to understand that which comes from other regions/countries that speak that language.
