So I believe you can legally play the following elder scrolls games for free

Arena
Daggerfall
Oblivion

I highly reccommend daggerfall but you need the right patches for it to work properly

Also you need to make sure you select skills you use a lot ilike running in custom character class creation f you want to level up quickly

I suggezt the 6 spell schools

Running
Climbing

Spell absorption
30 hit point die per level
Critical weakness to a lot of things
3 times intelligence in spell points