July 2019: This used to be bugged but seems to have been fixed. Feel free to comment if you run into any issues.
Paladins rewards you every day you log in, up to a maximum of seven days. This used to have to be done consecutively, which made it a harder, but now you essentially just need to log in on seven different days. Login bonuses give you free stuff, so if you plan on playing the game a lot, you may as well take a second to log in every day and get them anyway. It prompts you with the bonus after you log in at the title screen.
A few notes:
1. Often daily login bonuses are tricky internationally, as a day "starting" somewhere in the world is not the same across the board. A "day" in Paladins starts at 5 a.m. Eastern Time (ET), which is Hi-Rez's local time zone in Georgia, United States. So this means 5 a.m. Eastern is the earliest you can start the next day, and 4:59 a.m. Eastern is the latest you can claim a daily bonus to continue your streak before it resets. If you need help converting this to your local time zone, use Google or a time and date website
2. If you do not reset your game across two dates, the game won't let you claim your bonus until you restart the game. Example: You start playing at 3 a.m. Eastern, claim your daily bonus, then at 6 a.m. Eastern attempt to claim your bonus for the next day. It will show that you're allowed to claim a bonus, but clicking it will be unresponsive. Reset the game and log back in and claim it.