Reaching Rank 10 will take a total of 1875 XP, and unlocks:
Ability - Come Back Stronger; Horseman
Clothing - Millwright Boots
Horse Accessory - Birch 'Wide Belly' Horn
Weapon - Bow
Ranking up on Red Dead Redemption 2 online is achieved by doing pretty much anything. Taking part in matches/series, completing story or stranger missions, completing awards challenges, or even just hunting, fishing, and collecting herbs will earn the player XP.
With this in mind reaching rank 10 will pretty much come naturally. However if you want to speed up the process slightly I would suggest either competing in lots of matches, or just focusing on stranger missions.
Reaching each new rank will unlock a few items for purchase from in game vendors too, such as guns, clothing, and accessories. You can check the rank up unlocks, as well as your progress to the next rank by pressing the
button and choosing the "Progress" option, then the "Rank Unlocks" option. This will also allow you to see your past unlocks, as well as all future unlocks (so you know when you will be able to sport that snazzy new holster!). You will also receive a new Treasure Map every 5 ranks starting from Rank 10.