If you just want to buy a quality built reverse flow smoker and start cooking on it, the Lang 36" patio models are about as good as they get and right at $1,300, plus shipping. A few of the guys here have one and they love them. I don't know if it's big enough to cook a standard course for a barbecue contest, though.
The Yoder Cheyenne is about $900 if you want a traditional direct flow smoker and is a little bigger than the Lang.
Academy Sports has the Old Country Brazos smokers for about $1,000 iirc.
If you have the skills and the tools already (welder, cutters, hand tools, etc..) then certainly you could build a nice smoker for your budget using some scrap steel or old propane or water tanks. You also get the satisfaction of having built it yourself with your own needs in mind and can add the little extra touches that you wouldn't get from the larger builders. Check out the build forums for lots of how-to and build threads to see what others are doing.
But, having not used an offset stick burner before, you might not know what your workflow is or how you want it to function best. If you want to get your feet wet cooking with wood and figure out what you like and don't like about it, the Old Country Pecos Coal smoker is about $400 at Academy Sports and is as good an entry level smoker as is available.
If it were me, I would build my own custom smoker and get everything the way I want it. In fact I am planning to do just that. I just have to learn how to fabricate and weld first. :icon_mrgreen:
