Need a recommendation for a good ssd for gaming

This is good for the price.

PCPartPicker part list / Price breakdown by merchant

Storage: Crucial - MX300 525GB M.2-2280 Solid State Drive ($147.65 @ Newegg Marketplace)
Total: $147.65
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2018-02-22 10:28 EST-0500

Most games though can be placed on a HDD as it won't affect gameplay, just loading times.

Then I'd grab the 1.1 TB version of the SSD I posted above, plenty of space but like I said most games would be fine on your WD Blue unless you need the faster load times such as loading into a game of Battlefield before the match starts.

M.2 is nice as it connects directly to the motherboard however if you prefer SATA then there's a version of that.

PCPartPicker part list / Price breakdown by merchant

Storage: Crucial - MX300 1.1TB 2.5" Solid State Drive ($266.90 @ OutletPC)
Total: $266.90
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2018-02-22 10:43 EST-0500

And it's actually about $13 cheaper then the M.2 version.

Any reliable SSD will be good. Gaming doesn't do much writing to an SSD. Just reading. So, you don't have to worry about models with good endurance and great write performance.

As far a speed goes. Any good SATA model should be plenty. All the load time benchmarks I've seen have very little or no advantage to NVMe. Probably because of all the splash screens developers force you to look at.

That being said. You'll probably want good all around performance for uses other than gaming. If you want to go top of the line for your budget. You could get a Samsung 960 Evo 1TB. Then you'll have the fastest SSD you can get. If you want to save some money. I'd get a Samsung 860 Evo. You can go M.2 or SATA (2.5") on the 860 Evo. It doesn't matter for performance.

960 Evo: https://pcpartpicker.com/product/4cyxFT/samsung-960-evo-1tb-m2-2280-solid-state-drive-mz-v6e1t0
860 Evo: https://pcpartpicker.com/product/wd97YJ/samsung-860-evo-1tb-m2-2280-solid-state-drive-mz-n6e1t0bw

If you just want the most storage space for the money. Then get the Crucial MX300 1.1TB as suggested.

Your motherboard supports m.2 pcie devices at X4 speeds.
I suggest a Samsung 960 evo m.2 at 500gb It will be about $200. The 1tb version is about $450.
The pcie sequential speeds are some 5x faster than a good sata ssd.
That will show up in game level loads.
Other brands are cheaper, but The Samsung is the best performer.

Another nice thing about Samsung is that they have a free ssd migration app.
Install your m.2 device.
Download and install the Samsung nvme driver.
Run the ssd migration app to move your C drive from your current 120gb to the 960 evo.
Change your boot order and you are done.

Higher write endurance and slightly faster. Neither will matter for your needs. The Evo has a very high endurance already. The Evo and really any NVMe are so fast. That in real world use. A single user computer won't see any difference in performance. In some specialized workstation uses or in a server you might see a difference.

If you have to ask, the EVO is more than enough for you.

The Pro uses MLC - stores 2 bits per flash cell. The EVO uses TLC - 3 bits per cell. So in theory the EVO is a bit slower when writing files. In practice, they both cache writes as SLC (1 bit per cell), then slowly re-write them in MLC or TLC in the background. So the Pro only ends up being faster on large sustained writes.

The EVO also has shorter write endurance (number of writes you can make before the flash cell wears out). But unless you're running some sort of database that's generating hundreds of GB of writes per day, the drive will be obsolete before it wears out.

Think carefully about M.2 vs SATA. The higher sequential speed of the M.2 will only make a small, barely noticeable difference, but the price is much higher.

First, it's actually the slower speeds which dominate the comparison. Everyone concentrates on the sequential speeds, but it's actually the 4k speeds which matter the most. Say you have a NVMe SSD which is 4x faster at sequential reads (2000 MB/s vs 500 MB/s), and a SATA SSD which is 1.5x faster at 4k speeds (30 MB/s vs 45 MB/s). Give it a task where it has to read 1 GB of sequential data and 180 MB of 4k data. Which do you think will be faster?

NVME = 1000/2000 + 180/30 = 0.5 + 5 = 6.5 sec
SATA = 1000/500 + 180/45 = 2 + 4 = 6.0 sec

Despite being only 1.5x faster at 4k speeds (versus 4x faster at sequential speeds), and only reading 180 MB of 4k data (versus 1000 MB of sequential data), the SATA drive with better 4k speeds ends up being faster. Of course in reality, M.2 drives have about the same 4k speed as SATA drives. The point is that we really should be comparing SSDs based on their slowest benchmarked speed (usually 4k reads), not their fastest (sequential read/writes). And 4k speeds are still far, far below the SATA bandwidth limit and gain little to nothing from M.2 (we're starting to see some benefit for heavily queued 4k read/writes).

Second, we perceive speed in terms of how much time we have to wait - sec/MB instead of MB/s. So the bigger MB/s gets, the less difference it makes in terms of how much time you have to wait. Consider reading 1 GB of sequential data:

125 MB/s HDD = 8 sec
250 MB/s SATA 2 SSD = 4 sec (4 sec faster than previous)
500 MB/s SATA 3 SSD = 2 sec (2 sec faster)
1000 MB/s M.2 SSD = 1 sec (1 sec faster)
2000 MB/s NVMe SSD = 0.5 sec (0.5 sec faster)

Notice how every time MB/s doubles, the additional time saved is only halved? The bigger MB/s gets, the less difference it makes in perceived wait time. That's contrary to what you would expect just looking at the MB/s numbers. Or put another way, despite a NVMe SSD being 4x faster than a SATA 3 SSD, if you're switching from a HDD the SATA 3 SSD gives you 6/7.5 = 80% of the wait time reduction that the NVMe SSD will give you. You're paying a helluva lot of extra money for a NVMe SSD for that little 20% extra improvement.

The same problem affects car fuel mileage. The rest of the world uses liters per 100 km, but the U.S. for some reason uses MPG which is actually the inverse of mileage. So the bigger MPG gets, the less fuel you're actually saving. Switching from an old 14 MPG SUV to a newer 20 MPG SUV ("only" a 6 MPG improvement) actually saves more fuel than switching from a 25 MPG sedan to a 50 MPG Prius (a "huge" 25 MPG improvement). You know how people scoffed at the idea of putting hybrid drivetrains into SUVs? That's actually the best place you can put them.