Try St. John's Wort. It is a very cheap herb that I recently started taking for my own issues staying motivated and focused, and it really seems to have helped. Takes a few weeks of regular use before it gets going, though.
I think a 50 day supply was like $3 at Walmart here? Google St. John's Wort first though, it can have side effects mostly to do with Perscriptions. There are also those who think it doesn't do anything, but a lot of people in Europe swear by it, and it seems to pass the placebo test.