Congrats on beginning your crochet journey! You’ll be surprised at how easy it is to learn all of the different techniques along the way. My first piece of advice is to simply remind you that things may not come out perfectly right away, but keep practicing and don’t give up.
Now, for your question on joining balls of yarn; this really is not difficult at all. If you are changing to the same color yarn, you can get away with trying a simple knot. Just make sure that you leave long tails to weave in the ends when you are done. The simple thing about joining the same color yarn is that the knot is virtually impossible to see as long as you make it neat and tight. Now, keep in mind, this is something that the crochet purists might scoff at, but if you are still learning, this is a great way to go so you don’t get derailed on your construction process.
If you are changing colors, you’ll need to take a little more care. Look at your pattern and make a note of where you are to change colors. More often than not, you will find the color changes to be at the beginning or end of a row. My favorite method to change colors is really very simple: work to the last stitch of the old color and work that stitch until you have the last two loops on the hook. Pick up the new color and the old color at the same time and pull through the two loops with both colors. Now you can just drop the old color and give it a good tug while you continue on with the new color. This doesn’t just have to be done at the end of a row. In fact, you can change colors anywhere in your work using this method.
Play with joining balls of yarn, and remember that practice makes perfect.