ESO Mount Training & Increase Speed is easy and can be done daily and one method for a permanent gain of speed! This is a quick guide explaining what, why and how to do it!
Tamriel is enormous and every day you can feed your horse once which buffs certain traits! At level 10 you should a horse added to your collection. Each town has a Stablemaster, which is the NPC used to increase riding skills speed, stamina, and carry capacity via riding trainer tab which looks like a horseshoe. Each point can be applied every 20 hours at 250 gold each. You’ll want to prioritize speed > carry capacity > stamina. Stamina is used when getting attacked and or engaging sprint on your mount. If you run out, you fall out and can’t use your character for a couple of seconds. Consider stamina a priority over carry capacity if you’re a PvPer.
Another tip you can do to increase your mount speed is at level 10 complete the Cyrodiil Introduction quest by joining a PvP campaign and learning the basics of Cyrodiil. You’ll receive a mail at level 10 inviting you to do this. Next, you’ll want to complete the quest and take the Continuous Attack passive. This will give a Major Gallop at all times, increasing your Mount Speed by 30%. This applies inside and outside of PvP and is super helpful until you get your horse max speed. Additionally, Daily Reward logins contain horse speed so make sure to login every day!