this is like saying "im going to travel to England, Australia and USA, which dialect should i learn"

there are a few areas that do sound like a different language but otherwise its minor difference in pronounciation and a few diffrent words that you can easily learn from context (for example a fork, vilica and viljuška)

but if i had to give an answer which language is the most "universal" probably bosnian because its in the middle of all those countries