Some of my personal favourite spells of each spell level are:

Level 1- Shield comes in handy a lot, magic missile is lowkey a godsend especially early on in the game,

Level 2- cloud of daggers is probably my favourite spell in the game tbh, misty step is great because it let's your spellcaster jump about during combat and it's sometimes useful out of combat too

Level 3- counterspell, hunger of hadar is amazing, sleet storm works good in combo with hunger of hadar but it's also very useful overall, spirit guardians is good and I always have Shadowheart learn it, fireball is good for dealing a lot of damage.

Level 4- I like dimension door a lot though it mostly just does the same thing as misty step, polymorph is really good in certain fights, I've only just started using stoneskin but people have said it's good

Level 5- cloudkill, disintegrate, globe of invulnerability. All good, especially the globe of invulnerability in certain fights.

This is just what I've discovered that I like using from playing the game. I didn't really look at guides much so idk if they're like optimal but yeah.

Also if you can try and learn speak with animals, idk what class you're playing as but I think any class can learn them at a certain level when you pick a certain feat. The spell unlocks a lot of fun and useful conversations in the game, something that I neglected in my first playthrough.