The redesign, hiring someone, reinvesting, etc. I would be careful with reinvesting as there were testimonials here making thousands and also spending thousands, they were working for the sites with little money free from that circle.
You've got to constantly ask yourself, "What did I spend, and what did I get for it?" Over the years, you'll discover how to make the most money for the least expense. Also, if you're doing most or all of the work yourself, track your time investment because time spent on A is time you couldn't spend on B.
Which brings to mind another tip: know when to walk away. Some sites plod along for YEARS and then suddenly take off. Others are just losers - a bad idea, a niche you got into too late, etc. Working hard is great, but not on something that just doesn't have the right stuff in the first place. Better to acknowledge you made a mistake and start on something else than keep banging your head against a wall.