Update: I interrupt my own post to point out that there is no reason to do a shuffle if you don't have enough total points. Just figure out how long you need to wait, wait that long, and then shuffle.

So shuffle your points to be 25/36 of an hour from having what you need:
HP: 50-(25/36)*12
Mana: 107-(25/36)*17
Spells: 38-(25/36)*7
should do it, not counting some rounding errors.

Update: here's some ham-handed code (updated again to optimize leftover placement):

# Have/gain per hour
my @points = ([60,12,'HP'],[80,17,'Mana'],[31,7,'Spells']);

my @need = (51, 107, 38);

use List::Util qw(sum reduce);
my $total_have = sum map $_->[0], @points;
my $total_need = sum @need;

print "You have $total_have and need $total_need\n";

my $diff_need = $total_need - $total_have;
my $gain_per_hour = sum map$_->[1], @points;
print "You need $diff_need more, and you gain them at $gain_per_hour p
+er hour\n";

my $time_left = $diff_need/$gain_per_hour;

print "That should take $diff_need/$gain_per_hour hour(s).\n";

my @new_values = map $need[$_] - $time_left * $points[$_][1], 0..$#nee
+d;
my $leftover = $total_have - sum map int, @new_values;

# Put leftovers on furthest-from-goal
while ($leftover--) {
  my $slow = reduce {
    $new_values[$a]-int($new_values[$a]) > $new_values[$b]-int($new_va
+lues[$b])
    ? $a : $b
  } 0..$#points;
  $new_values[$slow]++;
}
@new_values = map int, @new_values;

for (0..$#need) {
  print "New value for $points[$_][2]: $new_values[$_]\n";
}
[download]

If the character is far from his goal, you might subtract more than you are allowed.

my @points = ([10,12,'HP'],[10,17,'Mana'],[10,7,'Spells']);
my @need = (40, 40, 40);
[download]

You have 30 and need 120
You need 90 more, and you gain them at 36 per hour
That should take 90/36 hour(s).
New value for HP: 10
New value for Mana: -2        <-----------
New value for Spells: 22
[download]

In that case, it is better to wait to do any shuffling. The total time required to achieve your goal will be longer if you choose a sub-optimal distribution of points. As I noted in my now-often-updated original post, there's no reason you shouldn't just wait until you have the required number of points, anyway.

---

Caution: Contents may have been coded under pressure.

This solution uses the same base idea as Roy Johnson's (summing the original stats), but uses an approach that won't give negative stats and doesn't suffer from rounding error. (It does this by quickly trying every possible combination of initial stats.)

use strict;
use warnings;

use List::Util qw( max sum );

my @stats = qw( hp mana spells );

my %rates  = ( hp => 12, mana =>  17, spells =>  7 );
my %stats  = ( hp => 60, mana =>  80, spells => 31 );
my %needed = ( hp => 51, mana => 107, spells => 38 );

{
   my $avail = sum @stats{@stats};

   our @parts;
   ('.' x $avail) =~ /
      ^
      (.*) (?(?{  length($1) > $needed{$stats[0]}  })(?!))
      (.*) (?(?{  length($2) > $needed{$stats[1]}  })(?!))
      (.*) (?(?{  length($3) > $needed{$stats[2]}  })(?!))
      \z
      (??{
         push @parts, {
            $stats[0] => length($1),
            $stats[1] => length($2),
            $stats[2] => length($3),
         };
      })
      (?!)
   /x;

   
   my ($result) = sort { $a->[1] <=> $b->[1] }
                  map { my $part = $_;
                        my $time = max
                                   map { ( $needed{$_} - $part->{$_} )
+ / $rates{$_} }
                                   @stats;
                        [ $_, $time ]
                      }
                  @parts;

   print(join("\t", @stats, 'hours'), "\n");
   printf(join("\t", ("%d")x@stats, "%.2f") . "\n",
      @{$result->[0]}{@stats},
      $result->[1],
   );
}
[download]

hp      mana    spells  hours
43      95      33      0.71
[download]

There's surely a better way of finding the partitions, but I don't know it off the top of my head, the method I used works, and the method I used is fast.

After an hour, do you gain 17 mana *and* 7 spells, or do you gain 17 mana *or* 7 spells?

Can you suffle your stats every hour, or can you shuffle your stats only once?

Hi.

They are ALL gained.

HP: 60, 12 per hour
Mana: 80, 17 per hour
Spells: 31, 7 per hour
[download]

You'd earn 12 HP, 17 mana AND 7 spell points per hour. In reality you don't earn the points at the turn of the hour, they are earned gradually over the hour (30 pts/hr means you'd literally gain 1 point every two minutes for a total of 30 that hour).

You can shuffle the stats as often as you want in the game but it costs gold each time you do it. So you wouldn't want to shuffle now and then in 2 hours shuffle again to get something faster. Best in one shuffle would be ideal.

Sorry for not clarifying