If you are thinking about did you buy too many EP. Fear not! Any EP you don't spend in exposition is converted to Story Points which you can use in...something. In a nutshell, your unused EP won't go wasted.
Anyway, it depends a lot what kind of merchant you are planning to be. Some merchants just need a shop => spend you EP on that. But if you also plan to produce stuff to sell => plan on using EP on infra.
You can always contact you mayor and ask is there anything the town can do for you and your business. Any flourishing business also helps the town.
No need to do everything yourself. If/when you take over an NPC merchant, he/she should already have a shop etc. So you probably shouldn't plan from zero.
You can buy the EP when you know what you need and what is available. Atm, you don't know neither... too early to plan how much EP is required. But you can alwys draw some basic plans.