What is considered ok for RAM latency?

Solution
It really does not matter.
Of course, lower is better at the same speed.
But higher ram speeds come with higher latency.

For gaming, the first consideration is to buy sufficient ram for what you will ever need on that motherboard.
Do not plan on ever trying to add more ram later.
It is not guaranteed to work.

You want documented ram compatibility. This is particularly important for ryzen which can be picky.
If you should ever have a problem, you want supported ram.
Otherwise, you risk a finger pointing battle between the ram and motherboard support sites, claiming "not my problem".
One place to check is your motherboards web site.
Look for the ram QVL list. It lists all of the ram kits that have been tested with that particular...
You can't just go by a specific combination of latencies, it varies a TON. It could be 9-9-9-18 on a 1600mhz DDR3 kit to 18-20-20-34 on a 3600mhz kit.

That's why it's always good to look up actually benchmarks.

But to answer your 2nd question about gaming, any memory is fine for gaming with Intel Skylake based systems, generally 2666mhz or higher is best.

But for Ryzen, DDR4 3000mhz/3200mhz at CAS 14-14-14-30ish is the sweet spot. Ryzen loves low latencies and high clock speeds on RAM for gaming.
 
It really does not matter.
Of course, lower is better at the same speed.
But higher ram speeds come with higher latency.

For gaming, the first consideration is to buy sufficient ram for what you will ever need on that motherboard.
Do not plan on ever trying to add more ram later.
It is not guaranteed to work.

You want documented ram compatibility. This is particularly important for ryzen which can be picky.
If you should ever have a problem, you want supported ram.
Otherwise, you risk a finger pointing battle between the ram and motherboard support sites, claiming "not my problem".
One place to check is your motherboards web site.
Look for the ram QVL list. It lists all of the ram kits that have been tested with that particular motherboard.
Sometimes the QVL list is not updated after the motherboard is released.
For more current info, go to a ram vendor's web site and access their ram selection configurator.
Enter your motherboard, and you will get a list of compatible ram kits.
While today's motherboards are more tolerant of different ram, it makes sense to buy ram that is known to work and is supported.

Fancy heat spreaders are mostly marketing, and you pay more for them.
They are useful only for record seeking ram overclockers.
Moreover, tall heat spreaders can conflict with some coolers.
Buy low profile ram.
All the major brands are good and will have a lifetime warranty.
 
Solution
You might want to read this article:

http://www.crucial.com/usa/en/memory-performance-speed-latency

Basically, buy ddr3200 or up, and let it find it's own timings for latency and you'll be fine.

More expensive ram has better timings, but speed is more important than latency.

I'm looking at ram with 14-16-16-31 (Corsair Vengance LPX 8gb sticks).

Make sure you are getting ram that is compatible with your motherboard! Most motherboard manufacturers have a recommended ram list on their webpage for each motherboard. If a particular ram module isn't on the list it MAY work... or you might have immediate problems or problems that show up later.

Good luck!