These are probably your best choices for new welders:
Lincoln Electric FCAW, I do not believe this machine is intended to be switched to GMAW
Lincoln Electric FCAW, with GMAW conversion parts
Hobart Handler FCAW, parts to switch to GMAW are available
Hobart Handler FCAW, GMAW conversion kit included
I don't know if it matters to you, but I believe that the Lincolns are made in Poland, and the Hobarts are made in the USA.
The first welder listed was the machine I started out on. I really liked it, and I kind of wish I had not sold it. It was made to fit a 10lb spool, and it was very light and portable for a wire-feed welder. With some tricks I was able to carefully weld a very small amount of 1/4" steel, but this machine was really at home on 16ga to 1/8" steel. If you want to do a lot of welding at once, or more than a very small amount of material above 1/8" you need to find a machine with a higher output and a greater duty cycle.
I completely agree that FCAW (flux-core) leaves several times as much splatter as GMAW (MIG), but I do not believe it is a bad choice for a project like yours. With practice, you can lay down beads that are strong and look great after a bit of wire brushing. Someone just starting to weld can save a bit of money by getting FCAW, be a little less strict about surface prep, and still do many projects just fine.
If you decide that you want to do more welding, you can either convert your machine to GMAW (if your machine has this option), or you can get a new machine all together. Of course with all of that said, if you are fine with spending the extra money, you probably wont regret getting a GMAW in the first place. If you are interested in GMAW, be sure to take into account how much a gas bottle will cost you, they can be expensive. If a used welder comes with a gas bottle, make sure your local supply company will fill it. Also be sure that the welder you get will plug into an outlet near where you will be welding, otherwise you should expect to pay an electrician to install a new plug.
If you are interested, looking for a name brand welder (Lincoln, Miller, Hobart, and Esab are popular in the U.S.) in the used market can get you a great, powerful, reliable, welder for a fraction of that machine's cost when it was new. Even if you are buying new, name brand is the way to go. Better quality, parts and repair services available, and a much higher resale value make the extra initial cost worth it.
Also, just as a heads-up, most of the GMAW welders will say that they can weld aluminum, which is partially true. In a more realistic sense, you wont be doing much aluminum GMAW welding without a spool gun and a 230V machine.