Max is referring to the game seed (the number associated with the save file that controls a lot of the RNG, including the traveling cart), not an in-game seed. So he wants a game seed to start a new game that gives the right RNG to get all those items from the cart. In 1.5, there's a place to enter the desired seed in the "new game" options.
@MaxWhite3790 , we had
a recent thread discussing how to get people to dance with you at the first Flower Dance. IMO, the easiest way is to avoid talking to anyone but Alex, so that you have a higher chance of getting quests for Alex on the Help Wanted board, since you can only get item request quests from people you've met. (There's a few people that are really hard to not meet because of cutscenes, and you can get mining/fishing quests even without having met Willy or Clint. But not talking to anyone else does make your chances a lot higher.)
Then you make sure to talk to Alex every day (and not when he's lifting weights - I'm pretty sure you get a "busy" dialogue then that gives you less points). And plant a bunch of parsnips, because parsnips are a liked gift. Starting week 2 when you have basic fertilizer, it's relatively cheap to plant enough parsnips that you'll probably get 2 gold ones a week.
- 20*23 points from talking each day, minus 10 because the reddit post I got this from said that that day 1 dialogue apparently only gives 10: 450 points
- One silver and one normal parsnip week 1, 2 gold parsnips weeks 2-4, and an extra 10 points on weeks 1-3 which you get on Sunday for having given 2 gifts: 45+49+56*6+10*3 = 460 points
This gives 910 points. Each Help Wanted quest is 150 points, and you need 1000 points to dance, so as long as you get one quest, you're good, without needing any loved gifts.
That being said, if you're picking a seed anyways you may as well pick one that gets you a loved gift just in case you get bad luck with the parsnips or forget to talk to him several times or something.
If you know how to code,
BlaDe's github has some automated scripts he's used to search for seeds before, but you'd need to modify them for the specific stuff you want.