Unless you are extremely lucky, or only if you are highly knowledgable, if you buy a pin and don't like it, you will most likely lose money when you go to sell.
So, study hard on what might appeal to you before you lay down your money. Take your time. Research.
Go to Papa and watch pinball videos. I did that for at least 12 months before I bought my first pin. Early on, there were pins I thought I would like but as I continued watching something else caught my eye. Eventually, I found the direction I wanted to go and I found a bunch of keepers.
You can find all kinds of good pins here. EMs. Early SS. DMDs.
Go to youtube and watch pins vids. Sometimes you can find a good video to watch. Sometimes you cannot.