Is it at all possible to make a more efficient version of this function that I've made?

What's written below is my code for distributing randomized stat points, made it over a year ago but abandoned it due to time constraints. I might reuse it but I need some fresh eyes to see how I could improve upon this function.

randomizeBase() This function randomizes base stats, the default base stats are all equal to 5 without the distribution itself. If a point was distributed, 1 should be deducted from the available points, but if it was already allocated there before, it should gradually increase each time a point was allotted. Available point deduction should be 1, 3, 6, 10, 15.

int availablePoints set the number of available points to be distributed.

int[] stat list to randomize stat distribution of primary stats

int[] statCounter list to determine or count number of times it's been distributed.

while (availablePoints > 0) While loop to check if availablePoints is still greater than 0.

switch(statCounter[randomIndex]) I used a switch function to check if a stat was already allocated by a number of times.

stat[randomIndex] += 1; Increases the stat point of a randomized stat.

availablePoints -= 1; Decreases the available points that can be distributed, increases sequentially.

  public void randomizeBase()
             {
                 int availablePoints = 20;
                 int[] stat = {0, 0, 0, 0, 0};
                 int[] statCounter = {0, 0, 0, 0, 0};
         
                 while (availablePoints > 0) {
                     int randomIndex = UnityEngine.Random.Range(0, 5);
                     switch(statCounter[randomIndex]) 
                     {
                     case 0:
                         if(availablePoints > 0)
                         {
                             stat[randomIndex] += 1;
                             availablePoints -= 1;
                         }
                         break;
         
                     case 1:
                         if(availablePoints > 2)
                         {
                             stat[randomIndex] += 1;
                             availablePoints -= 3;
                         }
                         break;
         
                     case 2:
                         if(availablePoints > 5)
                         {
                             stat[randomIndex] += 1;
                             availablePoints -= 6;
                         }
                         break;
         
                     case 3:
                         if(availablePoints > 9)
                         {
                             stat[randomIndex] += 1;
                             availablePoints -= 10;
                         }
                         break;
         
                     case 4: 
                         if(availablePoints > 14)
                         {
                             stat[randomIndex] += 1;
                             availablePoints -= 15;
                         }
                         break;
         
                     default:
                         break;
                     }
                     statCounter[randomIndex] += 1;
                 }
         
                 power += stat[0];
                 constitution += stat[1];
                 intelligence += stat[2];
                 agility += stat[3];
                 sensibility += stat[4];
             }

I really hope you guys can help me with this, any new ideas or methods are gladly appreciated. Thank you!