I die a lot unless I have a companion so I'm looking to get some tips from more veteran Elder Scroll players... thanks in advance!

I'm a mage. Defeating enemies is easy.

summon stuff

Doublecast lightning bolts to the face seem to do the trick.

And lots of kiting in the harder fights.

Use your surroundings and the Cast-and-Run tactic, specially at lower levels.

Pure mage, no armor, no weapons, no companions, no summons, took magicka on every level up. Level 7 now and no deaths. At level 5 I killed a couple giants without trouble. Quite simply, don't let them hit you. Run, dodge, weave, hide behind stuff, jump of ledges then turn around and blast while they walk around. In dungeons, be sure to lure stuff into traps. Mobs are dumb.

Playing on expert difficulty.

Basically exploit the poor AI with terrain.

Oh and use Flames like this -> Fire for half a sec, stop, fire for half a sec, stop and so on. It more than doubles its DPS and halves its magicka drain.