For a 400-600 chip $1/$2 cash set with minimal play restriction I think the minimum breakdown would start with:
$1 x 100
$5 x 200
$25 x 100
I believe 200 $5s is pretty much the bare minimum number of $5 chips you can get away with in a $1/$2 game as each player would start with a barrel of $5s and then when a player rebuys that player would just make change with someone at the table who has extra $5s. I think 300 $5s would be the ideal number as it's your workhorse chip, at least it is for the few hours, and then depending on how your game plays/how much stacked players rebuy for as the game progresses the $25s can become a co-workhorse chip, but for a bare bone $1/$2 set 200 $5s can work.
For the $1s I've hosted enough $1/$2 games to realize that even though we use 200 $1s, we easily could get away with 100 $1s without play restriction since in any given hand the $1s generally only come into play via the blinds and maybe the first raise. And once players get stuck and start buying in for larger amounts having 200 $1s on the table becomes less desirable to my players, so we start pulling some of the $1s off anyway.
How you ideally might divide up the remaining 200 chips in the 600- chip set depends on how your much bank you need to cover your game toward the end of the night. My $1/$2 game can get a little bit crazy the last hour or two, so if I were using a 600-chip set in my $1/$2 game I would go with something like:
$1 x 100
$5 x 240
$25 x 160
$100 x 80
$500 x 20
Having a $500 barrel makes sure I have enough bank for the game, but if your game has no need for $500s then you can use that barrel elsewhere in the set.
I have no experience with $.25 sets, I just throw some Fracs into my cash set and call it a day
