Time to go shopping! Go to the grocery store and get your items that are necessary for your recipes you've looked up and are confident in making. Go to the Dollar Store next to save money on cheap decorations that you'll only use once a year. The Dollar Store often puts its upcoming holiday's decorations in its first and second aisles, so go straight there to start looking for decorations. Everything here is cheap so you can get many decorations for less money. My suggestion is to get the biggest looking decorations. That way, it will look like you spent a lot of money to make this party great.
Also, try to buy 8-10 pumpkins from a local grocer for the party. These can act as great decorations and later I’ll tell you how they are useful in a friendly little competition for your guests during the party. Don't put off buying all of these things to the day of. Buy them a few days before so you can plan out where everything will go and you won't be rushed when making the refreshments.
Make your costume. To save money, go to thrift store and make your own costume. Halloween stores know that you will be scrambling to get a good costume quickly. You will pay handsomely if you wait to get your costume. Prepackaged costumes look more put together obviously, but it's one night. If you have a well-thought out costume, people will remember. They won't care how money you spent.
During the party, for entertainment, have one or two activities that your guests can choose from. I suggest watching a movie or having a pumpkin carving contest. If your guests want to watch a movie, make sure you have options when it comes to which movie. Ask around before the party if anyone has scary movies that they want to bring. If no one has any scary movies or all of their options are lame, find someone who has Netflix if you don't, and have them send off to get some scary classics. Some great movies for this night are Vertigo, Rear Window, The Shining, Psycho, Nightmare on Elm Street, and of course, Halloween. Make sure you make a spooky atmosphere where you and your guests will be watching the movie.
If your guests don't want to sit around and watch a movie, a fun alternative is to have a pumpkin carving contest. Get the 8-10 pumpkins you have as decorations and have people divide into pairs and have two judges. Set a timer for 20-30 minutes and let people carve! Your guests will have fun with friendly competition and it'll give them a chance to flex their creative muscles.