Baldur's Gate 3

Worth noting, if you're dual-wielding, you can sneak attack with a bonus action. (Go into your reactions and make sure Sneak Attack is set to always.)

AT is mostly about adding control and utility abilities to the Rogue; options to take enemies out of the fight, and aid/supplement your sneaking. Sleep, Colour Spray, Hold Person, Invisibility, etc, are your mainstays. Your unrestricted spells (ie, ones that don't have to be enchantment or Illusion) should probably be geared towards defence and mobility. (Shield, Misty Step, etc.)

To me the arcane trickster spells are more about utility out of combat.

But it depends on your party in the end. I combat, you need damage and controle, and some lvl1 spells are very good for control already. Fog cloud for example. Or grease, color spray and sleep. If no other spellcaster is casting this kind of spell, it can be handy.

But usually you'll prefer either defenses (at lvl7 the arcane trickster can get blur or mirror image), buffs (longstrider is exceptional for example), or other utility (disguise self, misty step, invisibility, charm person...)

Yeah I've always felt like Arcane Trickster is cool flavor wise but in game it just sucks. I assume when you do get second levels it picks up tremendously, though even then using your own action to setup sneak attacks isn't worth it either, for general skullduggery those spells will be a massive boon at least.

Maybe it would be better not to use combat spells at all? This is a balance of the regular features of a Rogue vs what is actually useful to them. The rogue deals a fair bit of damage in melee combat. No reason to need the shocking grasp cantrip.

Having the dash, disengage, or hide bonus action is great so long as you have for instance a spell that might augment one of those. For instance a spell like Fog Cloud or minor illusion to create an effect that would give you something to hide behind.

You're not high enough level yet to do this with other spells that are higher level on the spell list, but I think this is a matter of thinking about which spells work in conjunction with being a rogue.

Rogues are a bit squishy so using something for extra HP or a spell for protection might be in order (mage armor?). Find familiar might work just to do extra buffs/damage, and give you flanking.

You don't tell us what your race or background is so we can't tell if you have anything extra going for you, but I think you could have fun with this possibly if you change your intent from dealing damage with spells in combat to using spells to augment your class features in combat. Or those of the rest of your party.

As Arcane Tricker you absolutely want to dual wield, that off hand bonus action attack will be your best friend. Sleep + bonus action sneak attack is pretty much a guaranteed kill. Pick crowd control and defensive spells, Shield is an amazing insurance if you really do not want to be hit by a certain attack, Magic Missile is your go-to ranged finisher, Hold Person and Blur are both great offensive and defensive options, Misty Step for incredible mobility. And let's not forget Invisibility! Arcane Tricksters are also great enablers for other melee characters, let your wizard concentrate on Haste or other powerful spell while you handle Hold Person so your Fighter/Barbarian/Paladin can kill that unfortunate guy who failed his save in a single turn with guaranteed crits!

I haven't done a ton with Arcane Trickster, but I think you've got the general idea, at least at lower levels. Shield, Mirror Image, etc will increase your survivability. Invisibility is nice to deliver a sneak attack when you otherwise couldn't sneak up. In general, the AT's magic is utility-focused.

At level 9, though, you get Magical Ambush--enemies have disadvantage on saving throws when you're hidden. That's huge for spells like Hold Person, which can be hard to land. So you might end up doing more combat magic at later levels.