I am doing my first wedding cake soon and its a buttercream(my first as well I work mainly with fondant) and its 4 tiers. Will wooden dowels be enough support? Or should I figure out how to put a pvc pipe/board together?

Have you tried the sps system, it works great, its talked about alot on cc, there is a tutorial on cc, just go to the cake decorating forum and there are instructions on how to use it. Its at the top of the page. Its cheap and sturdy, I don't use anything else, and it would work with a 4 tiered cake.

You can use wooden dowels but you will need to make sure that you cut them perfectly flat especially with a cake that tall. I would also add a long center dowel down the middle. The SPS work great but the legs are four inches and to get the five inch legs you have to purchase a more expensive kit. My cakes usually end up 4 1/4 to 4 1/2 inches high so I have to trim the layers to even out the height for the legs. I prefer the Stress free cake supports. The legs adjust so you can achieve the height without having to cut dowels. It is a little pricey but well worth it. I have had the system for about five years now. I have purchased different sizes of legs as one of my cakes had a 3" bottom tier. I actually made a cake for a friend in exchange for the support system. The groom transported the cake on a two hour drive acrossed a bumpy dirt rode and it arrived in perfect condition. I also used it on the grass and log cake in my photos which my mother delivered an hour away and she had not problems. It does have an open center so you can still use a center dowel for extra support. You might want to check it out and watch the video they are wonderful. http://www.stressfreecakes.com/public/

Forgot to add I don't use the plastic plates pictured I use cardboard cake circles and non skid circles cut to the size of the metal rings attached with a little double sided tape.