If you want to quickly improve your public speaking skills, you need to get up in front of an audience as much as you possibly can. Each time you speak, you gain experience and expand your comfort zone. If you ask for and receive feedback, then you’ll improve even faster.
Toastmasters is good for this as it provides you with opportunities to speak. I recommend joining or visiting multiple clubs because you’ll address different audiences. You may get comfortable after speaking multiple times to the same audience so it’s good to mix things up. Also, different audiences will provide you with different feedback.
The one drawback to Toastmasters is it is a safe environment so if you want to take your speaking to the next level, you need to go somewhere where you’re not guaranteed positive feedback. Find service clubs such as Rotary or Lions and ask to speak at their meetings. Look for local business associations or Chambers of Commerce. The tougher the crowd, the tougher your public speaking muscles will become.