You can build what ever you want to build.
As for skills and being good as everyone else. That comes with practice.
When I first came here, I too looked around and thought to myself, "What the frak have I gotten myself into?" I just started building models that I like, posted build thread, and took on board what everyone told me about my models (good, bad, and indifferent).
I am far from being an expert (and I know that I have a TON of things still to learn about this wonderful hobby), but I am still cranking out models and enjoying every minute of it.
You should never let the advanced skills of other modelers intimidate you or scare you off. On the contrary though, you should be inspired by those builders and what they build and post to help you improve. I have gone through (almost) every thread here and learned quite a bit from MANY GREAT modelers. In the short time that I have been here, I would have to say that my skill have improved GREAT. With that being said, (and as I said before), I still have quite a bit more to learn.
So by all means, find something that you like and want to build and just do it. If you have problems, you can post your questions and problems in the forum, or if there is someone that (you think) can help you, send that person a private message (PM).
Just to let you know that my first kit was the Thunder Fighter from Buck Roger in the 25th Century. If you are interested, you can find the model here:
http://www.paperaviation.de/Science-Fiction/science-fiction.html
You had also said that you like BSG, you can find quite a few models here as well:
http://stevespaper.com/
Well, good luck with your builds and I look forward to seeing your work.
If you have any more questions, you can send me a PM.