A Firestick IPTV subscription should be judged by compatibility, support and reliability, not only by price. Check whether it works with the player you prefer before you pay.
What to check first
Ask what login format is supplied, whether EPG is included, how renewals work and how many devices or simultaneous streams are allowed.
Practical Firestick advice
Use services and playlists only where you have appropriate rights or permission. A professional-looking interface does not automatically prove that content is authorised.
Use IPTV apps and playlists only with sources you are authorised to access. A player app does not provide channels by itself.