"As an initial point, . . .", followed by "In addition to the forgoing, . . . ".
"Perhaps the most obvious point here is . . .", followed by "Further . . . ".
"A primary consideration when analysing this subject might be . . .", followed by "However . . . ".
OR start by quoting an existing argument. (e.g. "Plato believed that . . .") and follow it with a contradictory one. (Rousseau, on the other hand, argued that . . . ")
firstly - - I wd say 1st-ly, 2nd-ly 3rd-;y is SO clear that you shouldnt omit them
because
take a - b - -c - a is gonna be firstly - b cd be secondly or consequent on a and this should be signalled, C then wd be second or third point depending
so it signals a very clear logical progression which god know we need on AB for starters