HI Texan,
I am an ESL learner but a master in Vietnamese. I can be of help. For a beginner, three basic things to start with a new language are: pronunciation, sentence structure, and vocabulary. Vietnamese pronunciation needs 3 weeks to master (provided learner strictly follows the rules). Sentence structure and vocabulary can be found at
www.tinhhoavietnam.net. There is book entitled Cẩm Nang Ngữ Pháp tiếngViệt 'Vietnamese Grammar Handbook'. There you can learn vocab from A to Z and you will master 7 basic sentence structures. It may take you a while to master Vietnamese the sentence structures (in comparison with 5 basic English structures). Don't ever think about "dialects."
When I first learned English in 1958. I learned FrenchEnglish. In 1963 I learned PR English, 1965 I switch to American English. Now can speak some English dialects : New Yorker, Bostonian, Texan, Londoner....
What you need is basic, standard Vietnamese. With this you don't make any mistakes: The Northerners make terrible mistakes with the initial sounds: ch =tr, s=x, d, gi = z, n = l; the Central and the Southerners are not better; they don't make any distinctions of terms ending -n/-ng, -c/-t, low rising/high broken 'dấu hỏi/dấu ngã, and so on.
Remember it takes you forever to speak a second language natively if you are not a three year-old learner.
Hopefully these hints will help you learn the language authentically and linguisticallly.
Happy Holidays
Duy Nguyen