This is a list of spells that enhance the caster's movement excluding real transportation spells.
Great Fire Blast (Fire): Even though it wasn't its original purpose, you can use it as a long lasting transport which works in every angle.
Flame Body (Fire): It really just enhances your movement a bit, but it still counts.
Wind Ascend (Wind): It launches you upwards, and you can use another mobile spell afterwards to avoid the enemy or to launch bombs from the airs.
Scintillating Plasma (Plasma): It lets you move.
Bloodcurdling Blast (Nightmare): Extremely hard to ride because its hitbox it's very small, but in theory, you can ride it like the Fire projectile.
Spectral Embodiment (Spirit): Packed with a little bit of speed.
Rainbowifier Maximizer (Spectrum): If you really get in the way of your projectiles you'll get pushed.
Immolate (Phoenix): It lets you move.
Reaper's Lament (Reaper): You get lifted and then fall with an immense walkspeed temporally. This is a shield though, so it's main function is damage reduction and not speed enhancement, so running is faster than this spell's overall effect.
Bone Throw (Sans): Very hard to ride; you are more likely to get flinged because of the bone's intense spinning, but in theory, you can ride it like the Fire projectile.
Disorder Ignition (Chaos): After grabbing them, you can swap places with your enemy if you don't want to heal.
Soaring Upheaval (Dragon): You go flying while you shoot green projectiles, you can use this to go behind your opponent, inflicting damage and avoiding it at the same time.
Quill Daggers (Angel): The more you charge, the more you get pushed backwards. You can use it midair too.
Angelic Aura (Angel): Packed with a little bit of speed, and teleports.
King Slime (Slime): You become a ball and you roll around causing havoc.
Knife Barrage (Creation): You backflip and then you throw average knifes wherever you want. Works as a fast dodge.
Continuous Strikes (Creation): While your moving, the weight of the greatsword will enhance your movement as you inflict damage. Slightly faster than running.
If you were looking for spells like the Fire projectile to fly around, there isn't any spell like it, and the closest spells to its function are Bloodcurdling Blast and Bone Throw, but they are most impossible to use, so if you want it simple use Soaring Upheaval.