|Yes, that's really all you need.|
Ah, dowels, a topic that brings the blood of cake-builders to a boil for some reason.
I stick with your basic wooden dowels for most wedding cakes, and have never had a problem. That's because I do them the right way.
Whenever anyone online is complaining that their cake collapsed, it generally will come out that they dowelled the cake entirely wrong. And there are plenty of ways to do that.
Wooden dowels aren't the only option, obviously. You can use bubble tea straws (that makes me nervous but I know a lot of people who swear by them.)
You can also buy internal support systems that consist of plates and plastic pillars. For smaller cakes those are overkill, in my opinion. But if you like it, have at it.
I'll stick with the wooden dowels. They're simple, inexpensive, and as long as you use them the right way they work.
Something that I've noticed recently, though, is the tendency of some bakers on tv shows to overdowel their cakes. By the time they're done putting all the dowels into the cake, there's no cake left.
Last night I was watching a show and some guy was putting about fourteen 1/2" wooden dowels into a 10" cake. You've got to be kidding me! I felt bad for the person at the reception site who was supposed to try to find a piece of dowel-free cake when it was time to cut it.
The rule that I've always used was that the number of dowels for a tier should be an odd number (don't know why, might not really make a difference), and that you should take the diameter of the tier that's going to be stacked on top, cut that in half, then use that number for the number of dowels. If the number is even, you can add one dowel (or subtract, depending on your cake's design.)
Of course, you should take the number of tiers that will be stacked on top of the tier into account, but that's a general guideline.
There's no reason to make swiss cheese out of your cakes by inserting too many dowels. Remember that you still want to have something edible left over after the dowelling and stacking process is done.