I have only ever picked Expansion twice.
First, as Portugal going Exploration -> Expansion, only picking the very first idea until the Age of Exploration ends for the extra colonist while you have +50 settler growth and +3 dev per colony (you can use spare admin points to increase tariffs instead). Then immediately dumping the idea in favour of economic or humanist (depending on you want to focus new world or africa/asia first).
Second, I picked it recently in a Tall Japan colonizer game. Idea being that I house ruled myself out of doing anything but developing and colonizing (+taiwan and korea), taking advantage of -30% dev cost of national idea / shinto / mandate of heaven


If you want to actually play the game and do anything but colonize, virtually every admin group is a better pick. In the long run, even the +1 colonistis is barely worth it for colonizing since other groups will let you earn more money faster, and thus run an extra colony above your limit.