There is nothing wrong with a steel framed bike. Most of the high end builders (Sachs, Vanilla, IF, Waterford) work almost exclusively with steel.
There is a vast difference of quality between a gas pipe Huffy and an 80's era Japanese road bike like Univega, Fuji, etc. The frame material has no difference in efficiency. It's how that material is applied. I've ridden plenty of crappy heavy plain gauge aluminum bikes, noodly titanium bikes, and absurdly stiff and uncomfortable carbon bikes. Butted cromoly tubing from tru temper, renyolds, Tange is going to give a more comfortable ride over long distances as compared to aluminum though.

I'll offer this caveat- as a newish rider, it won;t really matter- your experience level is not going to favor one bike frame or another. You will not be buying crap if you end up with a cannondale road bike from the early 90's. A bike shop brand bike is where you would start with. Specialized, Trek, giant, Raleigh, etc. and the older Japanese brands like Univega and Fuji. I'd see what the local bike shop has, but Craigslist is going to be your best option with the price range you are looking at. Used bike shops are an option too.

With a CL bike, expect to pay another $50-100 to get it in long distance road worthy condition. even if the dude selling it says it's fine, it's best to get a second opinion, and a tune up at the local bike shop.

if you want, post a couple CL ads of the bikes you are looking at, or DM me. We can provide some info, and questions to ask.