Advice on how to stock up on an entire business professional and casual wardrobe?

Just got a job that requires me to dress both business professional and business casual, only issue is I own almost none of these types of clothes as I usually dress in street wear. That being said, I am looking to buy a couple suits which I will do on my own, but also need to know what exactly can be classified as business casual or professional. I sort of like the dress pants with button up shirt and tie with a sweater vest over it look, but I am not sure if that is considered casual or not. Any pointers in the right direction?

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