[Skarg]

I've usually handled it by having whoever wins initiative chooses whether they want to move before everyone else, or after everyone else.

Then for "everyone else", the highest initiative roll also gets the same choice within the remaining groups.

e.g.:

Four different groups A, B, C, and D are in the same combat.

They all roll for initiative, and say A rolls highest, followed by B, then C, then D.

A gets to chose to move first or last.

Then B gets to choose whether to go before or after C and D.

Then C gets to choose whether to go before or after D.