If you want to change your Mundus Stone buff, all you need to do is travel to the wayshrine that is closest to the desired Mundus Stone and make the rest of the journey on foot or on your mount. You can get these via getting levels and by finishing certain quests.

Betnikh Skyshards. A lot of values change based on group composition, buffs, debuffs, and what kind of player you are. This is tricky first of all since we have a low stamina pool.

Elsweyr Shrine, Ancient Stone. Focus on filling up Mighty, then pumping up Thaumaturge.