Yeah....It's not like it's difficult to get all the items in that amount of time; let alone just the ones you need.
Pikmin one is great, and I suggest you get that one, it's about £10 or so (i THINK, can't be bothered to check)
Then get the 2nd on a later date.
Playing the 2nd Pikmin 1st, or simply just the 2nd game means you'd be missing out on a game, or wouldn't be able to appretiate the 1st after playing 2.