Yea you can buy the whole spooky set from the store. That's what I did.
That's also what I'd recommend doing. The Halloween event, just to collect the creepy series took me two days (I had to save, quit and TT to finish
). It's hard to find Jack when all your villagers are trying to poach candy from you.
I'd also recommend having 2 characters to get all the lollipops from all your villagers to get the whole creepy set.
Buy 2 sets of the masks 1 set per character.
Don't give Jack regular candy he will only give you spooky set stuff or masks.
You can try each mask on a at home villager to find the one that scares them. It's not just a one chance guess like they say. Just leave the house change the mask and then go back in.
Don't wear rare in game clothing stick to things you don't care about or QR clothes. Also, put up wallpaper and flooring you don't care about. Your outfit and wallpaper/floor are in danger of being "tricked" away from you.
Finally if you want to collect all the pumpkin heads loose to a trick being played on you without wearing anything on your head (hats, masks, or accessories.)
Lmk if you have more questions.