Welcome to the forum, glad to have you onboard!
I am Lionel O gauge guy for the most part, but I find DCC very interesting so I have HO too and I even have an N scale set. I still love my old HO DC trains too! I love toy trains. I always refer to them as toys, they are too much fun to be anything else! It does not matter if it is a state of the art modern $800 Lionel Legacy command control or a simple $20 DC locomotive, to me they are toys. I am proud to play with my toys!
Everyone seems to find a niche in this hobby and for me it has defiantly been the technology. You will find yours and if your like me it won't be your first choice. I started with conventional Lionel steam locomotives and after I had about half a dozen I realized I preferred the diesels. Then I got fascinated with the command control systems and rebuilding old HO trains. Christmas is a big part of my love for the hobby for me, that is always a constant. Playing with my Christmas trains is seasonal, but I am looking out for deals year round.
I always tell people to start slow, find out what you like best or if you even like trains before spending a fortune. With the space you have (more then many) you could do any scale.
I would start out with a starter set just to see how you like toy trains. Others recommend going straight for the top of the line and save yourself buying things you may out grow. I disagree, but I can see their point of view. This can be a very expensive hobby or a very inexpensive hobby, its up to you. I don't see my early purchases as mistakes, I see it as learning and I still enjoy the first set I got even though its relegated to being a Christmas train.
HO is the most popular and has the most plentiful inventory to choose from. N is second, but catching up it seems. O is a distant third. For me a big advantage to O is the size. Easy to work on and easy to see for my getting old hands and eyes. I am still able to work on HO, but the high end models have more detail then I can see. N is much to small for my hands and eyes.
I think this set is a great starting point for HO
http://www.amazon.com/Bachmann-Trains-Digital-Commander-Ready/dp/B000BPPNWE It comes with everything you need to be up and running in minutes with 2 DCC locomotives and a very basic DCC command control system.
This is a great starter set for O
http://www.modeltrainstuff.com/Lionel-O-6-30233-PRR-Flyer-Train-Set-p/lio-6-30233.htm It also has everything you need and it features Lionel's new Command control system "LionChief" it differs from other systems in that each locomotive has a dedicated hand held controller.
Both of those sets use easy to set up sectional track systems with built in road bed. Many modelers don't like those kind of track systems because they are not very realistic. But I see it as a great starting point and if you do want to go to more realistic track systems you can sell the set on eBay or use them to run under Christmas trees. I stull use both of those track systems because they are simple and easy to use. Bachmann and Lionel both sell expansion packs if you want to have more then a simple oval, most do. Because I stay with these track systems it was easy and inexpensive for me to build my inventory of track and trains by buying starter sets. Now I buy more specialized and higher end models but I still use the same track.
Here are some links to my local hobby shop and it is also a very big internet seller with great customer service and very competitive pricing. There are many good train dealers Train World in New York and Amazon are both good too, but watch the prices at Amazon, they can be inconsistent. If you are looking for something particular don't hesitate to post a thread and ask, you will be surprised by the level of expertise on this forum and someone will know where to find the best deal.
Lionel O Sets
http://www.modeltrainstuff.com/O-Ga...=Y&sort=3&cat=333&brand=Lionel&show=60&page=1
HO Sets
http://www.modeltrainstuff.com/HO-Scale-Train-Sets-s/334.htm
N Sets
http://www.modeltrainstuff.com/N-Scale-Train-Sets-s/335.htm
Train World
http://www.trainworld.com/
Amazon model trains
http://www.amazon.com/b/ref=amb_lin...rd_t=101&pf_rd_p=1485999602&pf_rd_i=276729011
There are many other dealers but those are the one I know best. There are other scales of trains as well but these 3 are the most popular and what I know best.
N, HO, O, DC, AC, DCC, or full scale Lionel Command Control does not matter what you go with, just have fun!
I am glad to see a potential new model railroader and I would be happy to help you any way I can, as would almost any one on this the BEST forum on the web!