Investing in yourself is not all about money. If that's all you have to give, you won't get much of a return.

What you pay money for, you should pay Attention to to see where your money is going.
What you pay attention to requires Focus so you can put all of you into the work.
If you're focused, bring the proper Energy to your work -- and halfway effort leads to halfway results.
All of the above don't just happen. You've gotta put Time into anything that's gonna eventually pay you back.

Invest wisely.