Hi
I'd get a 12ltr cylinder. It will stand you in good stead should you ever move to a twinset. You can do plenty of good dives on a 12 and if you have to, you could get a pony for redundancy. (I wouldn't, but thats just me
) If you start to do two dive days on boats then you may need two.
I would also recommend a single tank wing, but that really depends on what your instructors dive with and recommend. You might want to try a setup first, and many people on the forum can help with that, and a few suppliers too.
I also use Apeks regs, and can report no problems. Easily serviceable and standard hoses (for the most part). One thing no-one has mentioned is get DIN fittings, not A-clamp.
Finally, think about the diving you want to do, whether it be reef, cave, wreck, or quarry(?!), and look at the gear used by the divers who are already doing it. That should hopefully prevent purchasing something which you need to offload later.
Hope that helps
Andy