While T.J.L likely has the best answer, I'll add what can be accomplished with some extra (frankly ludicrous by level 3) GM help (within official rules).
The maximum without multiclassing is 13
You must choose a race that gives a cantrip.
[Total so far: 1]
Since multiclassing is not allowed, you must go Warlock
- Pact Magic
- Pact of the Tome
[Total: 6]
There are two options for your patron:
- Undying (SCAG)
- Celestial (XGtE)
- Sacred Flame (light included later)
[Total: 7]
Your GM gives the Training reward (DMG 231) twice for these feats:
- Magic Initiate
- 2 cantrips of any one class
- Spell Sniper
- 1 cantrip of any class that has an attack roll
[Total: 10]
You need these Magic Items:
- Staff of the Magi
- Ring of Shooting Stars (non-Drow and non-Half-Drow)
- Dancing Lights (Note: can only be used in dim light or darkness)
[Total: 13]