After playing few first games what I do not like is the fact that characters level very fast what means they become powerfull very fast, so I implemented some house rules to slow down leveling (after all there is only 12 levels) and make game more challenging.
Cost of leveling should increase with time, its obvious that getting from first to second level should be much easier than from tenth to eleventh, so:
level: cost:
0 --> 1 6
1 --> 2 6
2 --> 3 6
3 --> 4 7
4 --> 5 7
5 --> 6 7
6 --> 7 8
7 --> 8 8
8 --> 9 9
9 --> 10 9
10 --> 11 10
11 --> 12 10
This is how I am plying it. In my opinion is a bit more fun when we level characters longer rather than just walking around with maxed levels already and one shot any enemy . People can test other variations of this idea like example even more slowing down leveling process:
level: cost:
0 --> 1 6
1 --> 2 7
2 --> 3 8
3 --> 4 10
4 --> 5 11
5 --> 6 12
6 --> 7 14
7 --> 8 15
8 --> 9 16
9 --> 10 18
10 --> 11 19
11 --> 12 20
(with barely 6th level I finished sucessfuly a game with this system)
enjoy .