Let’s play with some of the spell rules a bit…. How about one where you gamble!
Fortune and the Bold
1st-level necromancy
Casting Time: 1 action
Range: 100 feet
Components: V, S, M (a die)
Duration: instantaneous
You point at a creature in range as the forces of life and death coalesces around the hapless creature. That creature may elect to make a Charisma saving throw. If the creature does not, that creature takes 2d10 necrotic damage. If the creature does make the roll and succeeds, that creatures heals 2d10 damage. If the creature makes the roll and fails, that creature is dealt 4d10 necrotic damage.
At Higher Levels. When you cast this spell using a spell slot of 2nd level or higher, the damage dealt and healed increase by 1d10 for each slot level above 1st.
Thoughts?
Throat Punch Games 
I thought necromancy didn’t heal..? Also, like that it is both. Haven’t seen that in a long time in d&d. Good idea but I think you have the school wrong.
I wasn’t sure which school to do it in. 1st ed cure was necromancy and this does do damage, so I though necromancy. What school would you think?
Also, with that much damage, I think it should be a higher level spell.
I thought that the possibility of healing took down the overall damage dealing potential of the spell. Witchbolt does 1d10 every turn for as long as the creature is alive, so I didn’t think it was too far off.