I understand where you are- I was really on the fence as well.
Thing is, nothing protects like an MX boot, and your ankles are one of the most vulnerable areas when learning to ride offroad (or being an expert offroad for that matter).
Have you considered "hinged" MX boots? Gaerne SG10/SG12 or Sidi Crossfires come to mind. Problem is, these go over your $300 dollar budget. I personally have the Crossfires, and they are comfortable and easy to walk in. They are NOT easy to run in. I have been in rain and through water crossings with them and my feet stayed dry, though they are not supposed to be waterproof.
Maybe try to find a decent pair of cheaper hinged boots with MX protection levels. I told myself that since I had no idea what im doing offroad, and i have no health insurance, I had better get the best boots money can buy- I dont regret it.