Hey :)

I was invited to join a high level campaign and decided to go with a Hexblade/Pact of the Blade Warlock. 

To gain a Fighting Style and some extras I went 3 levels into Fighter as well wich makes me lvl 15 in total with 12 Warlock level.

Any recomandations on Spells? I really can't decide and its also my first spellcaster ever :"D

Thanks a lot!!

Hex is a must have, with relentless hex and maddening hex invocations, fear (could.give you advantage), Armor of Agathy's  (THP and damage to those that hit you, 4th level shadow of Moil, spirit shroud, enervation , for the 6th level mystic arcanum.....otherworldly form.

I focus on concentration spells since you get few slots and can maximise spells that last 1min or mpre.just to name few.....

To that end, (if you haven't already) taking those fighter levels first gets you a nice boost to con saves.

Concentration spells are great because you have a limited number of spell slots.

I recommend Hex and Shadow of Moil for great concentration spells.  For a spell that isn't concentration, go with Synaptic Static.

For great utility spells that scale up very nicely in higher level spell slots, go with Invisibility and Fly.