Ok here is my advise on flyfishing from a floattube.
The first thing you need, is an inflatable pfd, so that you wear it, at all times. The very last thing you want is to be stuck out in a lake in waders in a tube and get a hole in it. I have seen it and it has happened to me.
As far as flyrods from a float tube, if you are not an expert caster, I would start off with a heavier rod, you won't be able to cast as far sitting down at first. A stouter 5-8wt 9ft rod will help. I love my 1,2, and 3 weights, but in a tube for a beginner its very hard.
Get a spares spool for your reel if you don't have one. Have floating line on one spool and a sink tip system on the other spool. Don't go cheap online. Plan on it costing from $50-90 for your fly line setup. The reason I say get good line, is because it makes your casting so much easier.
It is hard to say much about flies without knowing the lakes, but I always have a lot of green careys, wooly buggers, and elk hair caddis dry flies with me when I fish for trout.
Get a net and hook it to the back of your tube, its hard to land fish at first in a tube because your rod is so long and you have to get the fish to your lap.....
That should get ya started. Float tube fishing is very exciting.