The Tony and Keith Photographic Workshops really stress the necessity of a good tripod. Keith never had to be convinced because he owned a camera store and too often saw the results of the use of a bad flimsy one. On the other hand, Tony's first tripod and ball head were so-so at best, but he lived with them. Whenever Tony had saved enough money, he always found something more important to buy than a plain old tripod. Whenever there was heavy wind, all he could do was push down on it to make it steadier.
It took Tony a long time to realize that he finally had built a good house on a weak foundation! When he did buy a really good one, he purchase a 4-section 6-foot carbon fiber instrument. He knew, after using it a couple of times, that he should have made that decision sooner.
A good tripod will cost somewhere in the range of $300-600. There really are no exceptions. The range is usually the weight difference. Aluminum ones weigh more but are less expensive than the lighter-weight carbon fiber tripods.
Remember that the tripod is only half of the foundation. The head assembly that lives between the camera and the tripod is just as important. You can upgrade your ball head separately for about $200-400. You may see a future post on this as there are so many different ways of connecting your camera to your tripod.
With the purchase of the head and tripod upgrade, you will see a marked improvement in the sharpness of your images. Borrow or rent one and see the difference.
When Keith and Tony are out on our workshops, we have let people try our tripods. They are very convincing demos.