My Homebrew d300 Wild Magic Surge Table. When you roll on this Wild Magic Surge table you roll BOTH a d100 and a d20 at the SAME TIME. The d100 shows you which row to go to and the d20 shows you how Good/Neutral/Bad the effect will be.
D20 Result: 1-5 Bad, 6-15 Neutral, 16-20 Good
If any effect tells you that the Wild Magic Surge will always be a certain type (Good/Neutral/Bad) then you do not need to roll the d20 and only roll the d100 to see what you get.