I'd say buy a WSM off craigslist for $30-125 as a first smoker (they are available often). It is as affordable as a UDS, you won't have to build it, its finish won't rust, it'll already be seasoned and had enough cooks on it to get of the internal reflectivity. It should work like a charm right after getting it home.
For UDS style cook just remove the water pan. For a PBC style cook, just remove the water pan and get the add on item for hanging meat from hooks. (or build one with bent and welded rebar)
The WSM stands in the happy middle ground of what you are asking for. One one side you have the ultimate, set it and forget it: the pellet smoker (but it is weaker on the smoke flavor). On the other side you have the offset smoker which requires the most amount of work, tending a fire, but produces some of the finest tasting smoke. The WSM stands in the middle of these two being pretty much set it and forget it (with some minor tweaks during the cook here and there) and produces a more flavorful and stronger smoke flavor than the pellet smoker. You'll learn a lot more about BBQ and fires using the WSM, versus the pellet smoker, and it won't cost you hardly anythign compared to either the offset or the pellet smoker. It's often good to start with less expensive items, especially one such as the WSM, which is an awesome cooker that has won national championships.