Silent Image is a terrific first-level spell. With it, you can:
1. Make an opaque wall of ghostly spirit-forms. This gives full cover--useful vs. ranged attackers, casters, and gazers--and makes it unlikely that anyone would want to touch it ("interaction" is a requirement before a target gets to make a Will save to "disbelieve" the wall).
2. Create a scout who can reveal ambushing monsters by drawing attacks. Like, say you come upon a bridge. Rumor has it, a monster lives under the bridge. So send the party scout--an illusion--sneaking ahead first. If you're lucky, you'll draw a spell attack, a breath weapon, or other high-value resource from your opponent.
3. Scare away monsters. Use Silent Image to "summon" a dread wraith. If your (lower level) opponents have any sense at all, they'll take off. Bonus: since wraiths are incorporeal, your foes won't think it odd that their weapons pass right through.
Other solid, useful spells that you'll cast over and over:
Color Spray, Mount (explained earlier--terrific source of muscle power/decoy/instant roadblock), Enlarge Person, Magic Missile, Grease, Protection From Evil.
Great spells to carry as scrolls (at least 2 scrolls each): Alarm, Hold Portal, Endure Elements, Shield, Comprehend Languages, Detect Undead (useful for tomb raiding; it penetrates through doors and up to a foot-thick stone sarcophagus), Floating Disk, Sleep, Ventriloquism, Animate Rope, Magic Weapon (carry at least one scroll for each party member).
That's a lot of scrolls but hey, the feat is free and they're cheap. And when you need one of those spells, you NEED one of those spells.

Make fresh copies every level if you can afford it, or every other level if money is tight.
-z