Ah, pikmin... One of my favorite games. Yellow pikmin are mostly useless without bomb-rocks. Though they are handy for getting to high places. My main tactic with them is to use them as sacrificial bombers on things that would normally take way to many Reds to kill. Just get a pair of bomb-holders eaten and that is usually enough to cause major damage.

Reds, Are fireproof, tough,and do a lot of damage... yet have a stupid tendency to run into water trying to follow you.

Blues can act as life guards, whenever I had a whole lot of the other colors moving around near water, I'd line the water on the path with blues.

And finally every victory needs a near the end of the day have 4 of your pikmin carry you to the onion, where they will make FIREWORKS!

Anyway I'd recommend a whole day to pikmin development, two if you can spare them. But for that You need to get way ahead on part finding. And you should always make those population expansion days count. If you do take the two day route. Leave the pikmin from the first day in the ground till the second day. They will grow flowers, though you should probably test this as I haven't played in a while.