Start with the sample when taste is uncertain
A discount helps only after the manga itself feels right. If you are unsure about tone, art, or pacing, read the official sample before thinking about price.
The sample protects you from buying a title that is cheap but not actually a good fit.
Start with the discount when the title is already known
If you already follow the series, price and timing can move to the front. Confirm covered volumes, coupon terms, and final checkout price before deciding how many volumes to add.
That flow works best when taste risk is low and purchase conditions are the main question.
Use both checks for new candidates
For a new title, the safest route is sample first, discount second. That keeps curiosity and budget in the same decision.