I use CEX and its a GH (gigahash, aka mining power) trading platform. Market prices are paid for GH, a lot of helpful people in the chat box there and it's really catching on. I have about 8GH on there at the moment and I trade pretty frequently.
The trading allows you to trade up to more GH as the price drops (as the difficulty goes up the GH produce less BTC) but since it is a falling market and still has some upside swings, it's pretty easy to get the hang of, and of course you can just buy and mine and keep mining if you expect the next difficulty change to be less difficult to mine, or if you expect BTC prices to get to 10k within a few months.
I have been able to increase BTC and GHs by trading pretty much flat and buying in lower (you keep the BTC you mine while you wait for your exit point)
The best thing though, is that the GH are yours forever. (unless they go out of business I assume) you pay a percentage for electricity and maintenance.
you can get started with .000001 BTC
the link is in my signature (oh yeah you make a small bonus on referrals to)
Alternatively, you can just buy 1GH for about $11 for 1 year from butterflylabs.com no idea when they will start mining for you, but it's another low-cost option and they take USD
That sounds genius whole new business models are popping up around all this. I think that event though the Bitcoin bandwagon is in overload, cryptocurrencies are far from mainstream and I thin kanyone getting in right now and learning will be in a good position when there is mainstream acceptance.