Ability scores

Dexterity remains the main Rogue ability. Intelligence becomes the important secondary score when you select spells that use attack rolls or saving throws. Constitution remains useful for durability and concentration.

Weapons and Sneak Attack

A finesse or ranged weapon remains the normal Sneak Attack delivery method. Arcane Trickster magic should usually create advantage, concealment, control, or safer positioning around that weapon attack rather than replacing it with a spell attack.

Action economy

Use spells to create advantage, concealment, control, mobility and infiltration rather than trying to become a full Wizard. Keep a finesse or ranged weapon available because Sneak Attack still applies to weapon attacks, not ordinary spell attacks.

Skills and Expertise

Stealth and thieves' tools are natural Expertise choices for infiltration, while Investigation supports traps and clues. Arcana can fit the magical identity, but Expertise is most valuable when it reinforces the tasks your party expects you to solve repeatedly.

Common mistake

The common mistake is trying to play the subclass like a low-level Wizard with a Rogue attached. Its spell progression is limited, so the strongest choices often improve stealth, control, defense, mobility, or Sneak Attack setup rather than competing with full casters for raw spell output.