In our quest to strip down the classic spells of D&D to the essentials, we have a new contributor, JD Jarvis, whose picks don't change our 1st level selection smuch but get added in to the next 2 levels.
Invisibility is the clear winner for super wizards everywhere, with 4 out of 6 desert-island spellbook compilers choosing it. Behind it we have a pack of four, each tied at two picks: Web, Levitate, Mirror Image and ESP.
Mirror Image is cool ... but it serves much the same function as Invisibility. Some people would give ESP the heave-ho on the grounds it's a plot spoiler. I just nerf it into Detect Thoughts, and if the being fails a Mind save the caster gets to sample one thought from its stream of consciousness. Levitate and Web, together with Flaming Sphere, are the more physical spell effects that would anchor the Day list if I picked three "Day" (straightforward) and three "Night" (arcane) spells. But with Feather Fall being expanded to Weightlessness, Levitate is too much like that and too much like a certain spell coming up next level. So the final three are:
ESP: Overnight recovery at (caster) level 3
Invisibility: Overnight recovery at level 3
Web: Overnight recovery at level 3
By the way, I'd probably pick Knock/Wizard Lock for the third of the level 2 Night list.
I'm not sure of the wisdom of allowing turn recovery for some of these, but the levels in question are high enough that the "Basic" rules don't have to worry about that.
The level 3 spells ... well, Fireball and Dispel Magic are clearly the A-listers, with all 5 contributors choosing them. This is where the limitations begin to grate; Fly gets 2 votes but there are some other strong contenders, like Haste, Clairvoyance and Monster Summoning. The Day list would really start to shine here with Fireball, Fly and Haste, while for Night effects, the ability to summon a stronger monster, dispel magic and use clairvoyance would have to do. For now, let's go with:
Fireball: Overnight recovery at level 5
Dispel Magic: Turn recovery at level 5 (with no re-tries to dispel any one effect)
Fly: Overnight recovery at level 5
Next: up some comments on how this approach would fit into a class system, plus spell cards!