Building a Rig- First timer in need of advice

[Artorias]

I've upgraded several existing systems in the past but this would be my first time building one from scratch and need some advice.

Below is something I threw together with some research but certainly no price research yet.

PCPartPicker part list: https://ca.pcpartpicker.com/list/gKjNCy

CPU: Intel - Core i7-7820X 3.6GHz 8-Core Processor
CPU Cooler: Corsair - H90 94.0 CFM Liquid CPU Cooler
Motherboard: Gigabyte - X299 AORUS Gaming 3 ATX LGA2066 Motherboard
Memory: Kingston - FURY 16GB (2 x 8GB) DDR4-2400 Memory
Storage: Samsung - 850 EVO-Series 500GB 2.5" Solid State Drive
Storage: Western Digital - Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive
Video Card: Radeon RX VEGA 64 8GB Liquid Cooling Video Card
Case: Cooler Master - HAF 932 Advanced ATX Full Tower Case
Operating System: Microsoft - Windows 10 Pro OEM 64-bit

1. What should I look out for when assembling in general for a first timer?
2. The system is for running games at 1080p. I want to keep longevity in mind, something to last at least 5 years with maybe a GPU upgrade 2-3 years down the line. Advice on CPU would be appreciated.
3. As you can see I plan to go almost entirely water cooled. This is something that is new to me and need advice with. What's a good manufacturer? What cases are compatible with two water cooled components?
4. Since I will be going mostly water cooled and looking at the watt requirements, would an existing 850W PSU from another system be adequate? The Vega eats power from what I have read, I'm not sure about the GPU yet.
5. Should I go cheap on RAM? What memory speed should I be looking for?
6. Should I go cheap on a motherboard? I don't care about SLI or Crossfire.

 

[Torn Mind]

You plan on doing video editing of gaming videos or are just strictly gaming?

Intel's Coffee Lake is about to come out at some point. The unveiling will be tomorrow but the actual time chips will be shipping might be in a month or so.

 

[Artorias]

Its strictly for gaming. I wasn't aware of a new CPU generation, are they changing sockets?

I plan to buy less priority parts in the coming month but I can wait for CPU or GPU parts.

 

[Torn Mind]

Its strictly for gaming. I wasn't aware of a new CPU generation, are they changing sockets?

I plan to buy less priority parts in the coming months but I can wait until new year for CPU or GPU parts.

Bascially, i7s and i5s become 6-core products on the mainstream platform. i7s get Hyperthreading, i5s do not. i3s are now true quad-cores. Socket is the same, but the the chips will NOT be incompatible with the Z270 chipset.

 

[MadOver]

If you overclock, get urself the OC-Formula... what a beast.