I try not to resort to hints until I hit Genius.
My arbitrary number is that if I am 12 points or fewer away from Genius, then I can use the Spelling Bee Buddy hints. I use the regular hints (like the 2-letter combos) whenever I hit a wall. Some days that happens a lot sooner than other days. I am *terrible* at Spelling Bees that don't have an "E" in the mix.