Reviewing some spelling bee study words can certainly be helpful before entering the competition. However, please remember that the words used from spelling bee to spelling bee can vary greatly. The judges are well aware of the words that are commonly used in competitions, and they are very well aware that anyone can just Google these sorts of lists. They do not want to make the competition impossible to win, but they are not going to spoon feed the competitors either.
What follows is a list from Merriam Webster of commonly misspelled words that is based off of the Scripp's National Spelling Bee competition.
The spelling bee study words above are a general guideline. However, the list used will depend a lot on both the grade that the participants are in, as well as the level of the spelling bee. The following links will help you find lists that are appropriate for the exact situation that you are in,
You can prepare as much as you want, and you absolutely should practice over and over again. However, remember that even with an extreme amount of preparation, you are never going to be able to guess and memorize every single word that will occur in the spelling bee. Remember, the point of a spelling bee is not for everyone to win. It is for people to get eliminated every round, so that one final winner can be crowed.
If you are frustrated during the competition, that is not going to help you. Try to kee frustration, anxiety, and nervousness to a minimum. Do not feel ashamed if you miss a word. At one point or another, everyone in the spelling bee competition, except for the winner, is going to wind up being out of the competition and sitting in the chairs with the audience. Furthermore, if you lose, it's just a game. You can try to be in another one at a later date.