Excel Formula that autofill an array with a list, based on an array

I'm trying to do a formula that within a range makes a list based on info on a specific array. What I need is an array that aufills this list based on the following conditions:

1)It has to be the first time the value appears
2)The value can't be " "
3)The value can't be repeated in the autofilling list

An example where the column A contains the data and the column B contains the formula.

Column A: | Column B:
AB12        AB12
            JH43
JH43        GO98
GO98        DT73
            AW64
AB12           
DT73
AW64

Im guessing the third condition should be !=(values from $B$1:B1) on B1, but I don't know how to make it different from a group of values. The second condition is !=" " and the first condition I have no idea how to do it.

Any help would be great, thank you.

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