For concentration try applying the tangerine technique when doing other task. Also remember to break down task which require concentration into managable parts. People with concentation skills tend to do things step by step. Give them a new task they will seem to lack concentration like anyone else. It's once you've determined what you have to do and in what order you need to do them.
For creativity, not everyone is meant to be creative some have better math skills others language. Not to suggest that you don't find ways to enjoy creative activities. You might find more fun in art, music if you realise you probably already are much more creative than you give yourself credit for.
On the whole I do suggest you focus on one aspect you would like to improve at a time. That way you can see results faster. In all it still comes back to actually spending time using the mental skills you talk of. Considering the brain is like a muscle you need more than one type of exercise to develop it.
In any case your best results will be with the first hour after that diminished returns. Consider also that you are actually depriving your brain of oxygen during that period. Longer periods could be more actually cause the reverse of the desired results, because you're not necessarily challenging the brain instead perhaps damaging it. The problem may not even become noticable for many years.
They say everything in moderation. Exercising any muscle for more than an hour a day, especially in the beginning, causes more problems than it's worth.
Alex
