He plays like a mage that casts a few spells and then is out of spell charges, so he has to start fighting with a normal weapon or spam some basic repeatable spell.
That is basically warlocks. Apart from your invocations you are generally reliant on the cantrip eldritch blast for combat. They do get less spells than wizards in return you get your spells back on a short rest and get eldritch blast the best cantrip in the game. It scales well enough that it is useful regardless of the level of your character. The warlock isn't a great choice if you want to be casting a lot of different spells.
Yeah, welcome to Warlock. Cast Hex as your bonus action, spam Eldritch Blast until the target is dead, repeat until combat is over. The good thing about Hex is that you can recast it without expending a spell slot so long as you keep concentration. If you're good/lucky, one spell slot can get you through the entirety of a day. It's not great for variety, but it's amazing for single target damage output.
