If u know how to roam, TF a great pick, bit weak early, but has high damage and tons of utility mid to late. of u have the intuition and skill to tele effeciently with your ult and are effecient at picking the right card. this guy can be pretty deadly. definetly a harder guy to use.
Ryze IMO is a bit ridiculous in concept but pretty strong, along with antoher i will mention, vlad, i think theyre a bit better top but can easily be played mid. He has fantastic burst and a VERY low cooldown CC. he is the king of spamming, and has tons of mana considering his abilitys scale with it. he is also 450 IP :)
Vlad is one of my favorite toplaners, but i occasionally take him mid. his late game is phenomenal along with his godly sustain from spell vamp and nonexistent mana. he does lack cc but makes up for it a bit with a really strong untargetable mechanic and immense damage and innate tankiness for a mage.
Viktor post rework i find quite strong. He isnt a bad laner, but late game he absolutely melts the enemy team with his deathray. i fond the combo r->q->e with a w on top is an easy instalkill off a flash in lane. he has really really high damage agter you get your e augment and items
this guy is really not meta, but i find alot of fun. he has a really strong CC with his w (cage with a hard stun) and is renowned for point and click instakills to other mages. i play him usually as an aggresive kill laner
another i play more top lane, but in mid he wrecks alot of viable picks atm like fizz. he plays a mode of the game that is 6v4, HUE HUE HUE. very tanky mage with great damage mitigation and poke
these are not really meta picks, but my post is just detailing my favorites and those i find FUN to play a few others i own and use occasionally are
along with some adcs if ur looking for more meta u can look to the previous posts, but these ones i find a bit more fun. at lvl 15 IMO meta shouldnt be at the top of your worries, hope this helps :)