second of all/second
“First of all” makes sense when you want to emphasize the primacy of the first item in a series, but it should not be followed by “second of all,” where the expression serves no such function. And “secondly” is an adverbial form that makes no sense at all in enumeration (neither does “firstly”). As you go through your list, say simply “second,” “third,” “fourth,” etc.
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