I'm planning to go for

CPU: Ryzen 5 1400 (160 USD)

GPU: GeForce GTX 750 TI (gift from a friend)

Mobo: MSI b350 Mortar (90 USD)

RAM: Corsair Vengeance LPX 8GB (1x8GB) DDR4 DRAM 2666MHz (85 USD)

Monitor: HP Pavilion 27xw (200 USD)

HardDisk: Not picky. Seagate for 50$ is fine with me.

My questions are:

1) Is the MSI B350 Mortar good enough for a budget build with Ryzen 5 1400? I'm quite happy with it as the price and the features seem to be good enough for me.

2) The RAM speed of 2666 MHZ. Good enough? I actually would love to go for 3200 MHZ. My only issue is the prices. So, is 2 4gb sticks with 3200 MHZ good enough for now or should I go for 1 stick 8gb but at 2666 MHZ?

What does the motherboard say about these numbers?

3) Quad-core. Does that mean I can install 4 RAM sticks?

4) My only constants in this build is the Ryzen 5 1400 (because I like it a lot) and the GPU (Because a friend is giving me his) . Any other suggestions to the other components?

Please keep it simple. It's getting harder and harder to understand and form a conclusion with the myriad of options available. Please only suggest an alternative you feel strongly is much better than my current selection AND it's price is very close to my current selection.

My total budget is somewhere around 500 USD. I live in the UAE so there's that :)