'Many of the races described below have a step adjustment to either a derived statistic or a skill. In the case skills, do not consider ...'

'In the case of skills ...'

Also, unless you really mean each race gets only one, it should be:

'Many races described below have step adjustments to derived statistics and skills.'

Also, I'd prefer ...

'In the case skills, Do not consider racial step adjustments when determining the Destiny cost of improving a skill.'