I typically follow these two pages:
neopets.com/~boochi_target (Known as Garet)
neopets.com/~Innocent (Known as Lefty)
Or you can check Reddit as well, some people post bets there too!
They seem to be pretty successful for me when I follow Garet or Lefty. And the older your account is, the better of course. Make sure to check the dates so you�re not placing the wrong bets. I typically will place my bets a few hours before the betting windows close at 1:30pm NST! There are occasional skip days as well depending on who you follow, so if you still decide to bet, be aware you may have a day where you don�t win anything.
Edit: I forgot to mention on Lefty�s page, they list a bunch of guides and other bettor�s pages, so plenty to choose from and lots of resources!
Good luck!