Mr. Smith, if you just want to smooth a cut, a Stanley #3 or 4 will do fine; if you also want to use it to true a line, longer is better--and the #4 is 1" longer and 1/4" wider. I tend to use whichever one is handiest to where I'm working. (If you don't care if the surface is dead flat, you might get by with a good block plane, like the Stanley #60 1/2.)
Stanley's are the most common planes--most everyone is familiar with them, and parts are commonly available either aftermarket or salvage. Information on tuning and adjusting is easily found. The numbers (#3, #4, etc) refer to sizes in the bench lanes (like smoothers and jacks) and to models in the block planes and specialty planes).
The #3s and #4s are common as dirt most places, so the cost isn't that great. Most days you can get a user off the 'bay for $25-30 delivered, and if you watch for a couple weeks, often under $20 delivered.
If it were me looking for a plane for odd jobs while stocking, I'd look for a Stanley #3 or #4. I'd want something between Type 5 and Type 18 (produced between 1997-1947) for parts availability. I tend to prefer "low knobs" (the front handle) because that was mostly what I've always used, and I try to avoid the corrugated bottomed planes (because I have trouble using them on thin stock, like the top of a forend or similar).
