This is a “warm-up”. These are the basic features of a 2016 desktop computer to catch you up to the latest. I’m  doing this in an overview fashion.

SSDs
By now, you should only be thinking about a Solid State Drive unless you are putting it into an old computer or REALLY need the huge storage for archives or the like.
SSDs have taken over. Even the slowest ones are about five times faster than mechanical drives. Just by cloning your boot disk you will change your boot times to around twenty seconds. And the fastest types might shave another three seconds, but that’s all.
I got onto some gaming sites and discovered that, no matter what processor or memory, or video card, the upper speed limit for data transfer during the game is below 600Megabits/sec. So any SSD with an SATA-3  6Megabit interface will be able to dish out data faster than the processor can handle it.
This may not always be the case, but it will be for the current breed of processors.
As a generality, physical hard drives get slower and slower as they get cluttered up. The latency times moving the magnetic head here and there greatly slow down the read times, not coming close to the theoretical sequential read times.
This is the advantage of SSDs. Switching from one part of the stored memory to another is just a matter of setting a few (transistor) switches. Problems with defragmented files have little consequence. This is the major advantage for your boot drive.
The M.2 specification was developed for mobile devices. The “drive” looks like a stick of gum, with a connector at either end. They’re getting popular on the latest motherboards. They cost about 1.5 to 2.5 times the cost of SATA SSDs, so you might have to spend an extra $100 for the cheaper ones. Their throughput is potentially about three times as fast, but might only shave a second off the boot time and not speed up actual compute time. You’d just have less storage for the money.
There are two faster specifications that use the PCI bus, and cost more and deliver memory at speeds even faster.
The point is to at least have an SSD for your boot drive and get 90% of the benefit.
You can buy a Samsung 850 500GB SATA 3 SSD for $150 on Newegg.com. Or you can buy a Samsung 950 256GB M2 drive for $182. Neither is THAT expensive. With older computers (like you and I have) there are PCI adaptor cards that mount the drives and fit many PCI slots.
Samsung 850 SSDs have a utility that optimizes their structure to your individual computer. This works better than the Intel speed optimizer. You can use something like a late version of Achronis to “clone” your existing magnetic drive if you want to just go faster with your laptop or desk PC. I did this three years ago. It’s easier and faster and cheaper now.
LGA 1151
The latest (generation 6) processors, Skylake-S CPUs, have the overclockers in a frenzy of excitement. With 14 NanoMeter trace size they have something like four times the density than Generation 5, Haswell CPUs, and much lower heat problems compared to the early Pentium fours of the 2000’s. So the emphasis is no longer on huge fan arrays and other extreme cooling solutions.
Until this 6th generation the clock frequency (system clock, base clock frequency) was tied directly to the PCI bus and couldn’t be messed with much, (maybe +5%) before things got unstable. PCI bus slots are the short slots commonly used for the graphics card. So the CPU “multiplier” had to be upped to get a faster CPU and Intel charged extra for a processor that had an “unlocked” (modifiable) multiplier. The voltage could be raised a small amount to make this work, but the processor got closer to overheating.
The 6th generation uses a different set of support chips, the Z170, that make it possible to again boost the BCLK (base clock) by about 30%, which is for a “locked” CPU. The “unlocked” CPUs (with a “k” or “x” designation) can use a raise in BCLK or the multiplier (or both) and a small voltage rise.
I’m not sure where it will go but most overclockers seem to be most comfortable with the (more expensive) K chip. By far the popular one is the i7 6700K, rated at 4.0 MHz, which is commonly overclocked to 4.7 MHz, costing $370 on Newegg.com. The regular i7 6700 locked chip can be operated at a similar speed with a boosted BCLK. The locked 6700 is “rated” at 3.4 MHz and costs $340, but it overclocks to almost the same 4.6MHz speed by just the BCLK boost (of a higher %), so some argue it is made “too good”. These simplifications have made overclocking easy and cheap.
The prices drop with big box stores batch purchasing, so it’s a supply and demand (price war) thing. You’ll occasionally see a 10-day price drop.
In either case you need a better CPU cooler, in the $30 range.
For those not wanting to overclock (many people) the standard cooler and cheaper CPU and regular memory (more later about this) and quiet operation are a great tradeoff. No worries, no problems.

It’s not that the newer processors are very much faster, but rather that they’re easier to work with and the new socket standard is clearly superior. So, this is about the new standard.

DDR4
This memory is faster than DDR3. In case you are not paying attention, a new chip standard, a new chipset (required) and new memory standard are a signal to start a new computer, as last year’s stuff will become obsolete. The stuff you can buy will be current for several years.
DDR4 has a nominal rating of 2100 MHz and 1.2 volts. You can buy it, up to 3600 MHz. The gamers say it is “diminishing returns” faster than 3000 MHz, given the current processors, graphics cards and games.

XMP PROFILES
Most z170 motherboards have the ability to use faster DDR4. You may have to switch a physical XMP switch or enable XMP in the BIOS. You would always download and “flash” the latest BIOS (and XMP files) after you first boot up the motherboard. “XMP” is the data of how your individual make and model of memory can be safely set to for fastest speed. The identity of the memory is read and the information is matched to this make and model. The very earliest boards came out with preliminary XMP data, so check the motherboard manufacturer’s website for the latest BIOS and XMP.

OVERCLOCKING SETTINGS
Here you should consult YouTube. There are different automatic settings for each motherboard manufacturer. ASUS, for example, has a one button automatic overclock. There is an example for each manufacturer and a few videos showing 4 or 5 main manufacturers. Just remember to enable XMP, if it’s not automatic, and use the “extreme overclocking” for the very fastest settings.
The main changes usually involve the BCLK, multiplier and CPU voltage changes.

GPUs (graphics processor units — video cards)
Most of the gaming sites either are using GTX980 or GTX970 graphic processor units (GPUs). The 970s for mere mortals and the 980s for those that can afford $650 for their viewing pleasure. Typically, almost any game can be played at 1080p and a high frame rate on a GTX970. There is a difference, but if you can see it, why are you reading this? You would already have better eyes than mine.
If you’re really into 4k video, then the 980 offers future-proofing for actually playing games in 4k resolution. The regular 970 can play 4k video, but not the 4k video games. If you’re into editing or creating 4k video, then GTX980 is a no-brainer.
No avid gamer in his right mind uses the “HD video” built into the i7 or i5 processors. They are fine for typical desktop applications like Word and Excel and seriously deficient when doing Photoshop. AutoCAD does ok on just an “ok” GPU for occasional use. But a “CAD drone” would climb the walls.

I hope this translates into something you can use in planning your next system.

Favorite Uncle Dean