I really like the Echo Timber calls. I wish I still had one but like all things calls come and go in my collection. They are a softer sounding call and a pretty good hunting call for that situation. I know a lot of guys that only blow timber calls, and I find that I use a timber type call %60-%70 of the time when hunting. I think and this is just my ever so humble opinion....If you want a call for "when you get good" as you stated I would buy it in a single. I like the sound of that call so much better as a single, and if you are comited to learn the call and are going to work at it you should learn the single. If you are good with a single you can blow any double or single well.
Now if you want to just get good enough to kill a few ducks with as little effort put forth to learn as possible. You should probably start on a double, but latter should you decide to learn a single you may have to unlearn some things, learn some others, and forget about a few other things.lol
When students ask me what to do single or double...if they ask. I tell them this same spill.... to me it depends on what kind of person you are, and how good you want to be.
just my .02
oh oh oh I almost forgot befor eyou settle on a regular timber try an Echo XLT I think it stands for extra loud timber. I blew one the other day and I really liked it. It is very versital and easy to run.