Right now, flights between Dublin and Edinburgh start at 17 euros one way leaving June 13, 14, 21, and are between 20 to 25 euros for the return trip a week from those dates.
That’s the cost without taking any luggage besides your personal item as defined by Ryanair and not choosing your seats. The final cost will be more depending on the options you choose.
You can also spend a bit of time on Skyscanner to see if you can find a decent price on full service flights that include seating/luggage in the price. Really depends on how you travel if Ryanair is best carrier.