Some things to consider:
-- You should always try to buy your RAM in pairs. That lets you use dual-channel mode, which will let your system run faster.
-- Ryzen systems do work much better with faster DDR4 RAM...but unless you're going to play a lot of games or do a lot of content creation, you probably won't see a whole lot of difference.
-- SSDs are pretty much a must for boot drives anymore. However, the 960 PRO line wasn't showing any 250-256GB models in stock, & the 512GB model is a lot more expensive. The EVO line should be more than sufficient for your needs. Plus, you'll want a 2nd drive (at least a 1TB 7200RPM HDD) for additional storage, as your SSD will fill up pretty quickly.
-- Yes, you would need to buy a discrete GPU for a
Ryzen build. However, for what you're going to do, you may not need a full Ryzen CPU anyway. So if you want to have future access to Ryzen CPUs, or even their upcoming Raven Ridge APUs (Ryzen-based CPU portion with Vega-based integrated graphics), you could always settle for a Bristol Ridge APU right now (Excavator-based architecture, but they fit into the same Socket AM4 boards that Ryzen does).
-- Without knowing what your budget is, it's also hard for us to make good suggestions on how to tweak your build.
As an example, here's a slightly tweaked AMD build for you:
PCPartPicker part list /
Price breakdown by merchant
CPU: AMD - A12-9800 3.8GHz Quad-Core Processor (€105.52 @ Mindfactory)
Motherboard: MSI - B350M MORTAR Micro ATX AM4 Motherboard (€84.61 @ Amazon Deutschland)
Memory: G.Skill - Ripjaws V Series 16GB (2 x 8GB) DDR4-3000 Memory (€154.90 @ Amazon Deutschland)
Storage: Samsung - 960 EVO 250GB M.2-2280 Solid State Drive (€130.76 @ Mindfactory)
Storage: Western Digital - BLACK SERIES 1TB 3.5" 7200RPM Internal Hard Drive (€77.05 @ Mindfactory)
Case: Fractal Design - Define Mini C MicroATX Mid Tower Case (€74.69 @ Amazon Deutschland)
Power Supply: Corsair - RMx 550W 80+ Gold Certified Fully-Modular ATX Power Supply (€96.48 @ Mindfactory)
Total: €724.01
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2017-10-11 21:27 CEST+0200
It's not a Ryzen 5 CPU...but since you're not really gaming, the performance loss will be small. And it comes in just under 725 euros (at least from German sources). Plus, if you decide later you want to drop a Ryzen (or even a Ryzen 2 or 3) CPU with a discrete GPU, or even drop in a Raven Ridge CPU, you're good to go.
By the same token, since you're not planning on gaming, you don't even need a Core i3 or i5 CPU, a Kaby Lake Pentium will do just fine (like the AMD A12, the Kaby Lake Pentiums are a dual-core/quad-threaded CPU, aka 2C/4T).
PCPartPicker part list /
Price breakdown by merchant
CPU: Intel - Pentium G4600 3.6GHz Dual-Core Processor (€79.90 @ Caseking)
Motherboard: MSI - B250M MORTAR Micro ATX LGA1151 Motherboard (€87.89 @ Amazon Deutschland)
Memory: G.Skill - Ripjaws V Series 16GB (2 x 8GB) DDR4-3000 Memory (€154.90 @ Amazon Deutschland)
Storage: Samsung - 960 EVO 250GB M.2-2280 Solid State Drive (€130.76 @ Mindfactory)
Storage: Western Digital - BLACK SERIES 1TB 3.5" 7200RPM Internal Hard Drive (€77.05 @ Mindfactory)
Case: Fractal Design - Define Mini C MicroATX Mid Tower Case (€74.69 @ Amazon Deutschland)
Power Supply: Corsair - RMx 550W 80+ Gold Certified Fully-Modular ATX Power Supply (€96.48 @ Mindfactory)
Total: €701.67
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2017-10-11 21:37 CEST+0200
This one comes in just over 700 euros, so it's roughly the same price range as the A12 build. And you can always pop in a Core i5-7600 or i7-7700 at a later date if you need more power. However, there are 2 downsides to going with the Kaby Lake build:
1. This particular board doesn't allow for overclocking (unlike the AMD build), so you should stick with the "locked" CPUs (i.e. those that don't have a "K" on the end). The solution would be to get a Z270 board (MSI's Z270 mortar only added about 28 euros to the price, so still pretty comparable). Of course, overclocking on mATX boards is probably going to be more difficult (the VRMs may not be as rugged, the case may not have the best airflow, there may not be as much room for a bigger fan on the cooler, etc.), but overclocking is usually more for getting better game performance than what you're planning on using this machine for.
2. More importantly, this build will
not be compatible with Coffee Lake. Although technically listed as using Socket LGA 1151, the pins for Coffee Lake are
not compatible with Kaby Lake or Skylake CPUs. So you'd be starting off with a "dead" socket that would limit your future upgrade options. You'd also have the problem of, if you wanted Coffee Lake, you'd have to wait at least a couple more months (possibly up to 5 or so) for the non-Z370 motherboards to come out, or pay more for a Coffee Lake system (30 more euros for the motherboard minimum, 60 more euros for an i3-8100 4C/8T CPU, 160 more euros for an i5-8400 6C/6T CPU).