If you wanna play games on 1440p:

1. GPU: At least get a GTX1070 for your build.
2. PROC+MOBO: If you are planning to overclock, get a Z-series mobo if you wanna go for intel so that even if you do not have the budget for an unlocked processor now, you can always upgrade in the future without the need of changing other mobo. Or wait for ryzen release of the R5 series.
3. RAM: Depending on your mobo choice, if you are not planning to overclock, just buy a basic 2133mhz ram (that looks nice ofc) because only Z-series mobo supports ram oc. There are H170/B150 mobo that supports ram oc by tweaking bclk but it won't matter much if you are not into overclocking anyways.
4. PSU: get at least 80+ bronze certified psu.
5. HDD/SSD: Any 1TB hdd is fine. SSD can be put on hold if you are on the edge of your budget.
6. Case: Any case that you like. This is a very subjective matter.

Example build:
GTX1070 Strix rm1899
Intel i56400 rm800
Asrock Z170 Extreme 4 rm655 (can swap to B150/H110 and go for better proc if you are not going to overclock)
HyperX Fury DDR4 2400 1x8GB rm303 (can swap to 2133mhz if you are not going to overclock)
Superflower leadex 550W 80+ gold rm429 (can swap for at least cheaper 80+ bronze but this here is Tier 1 psu which is very very good one)
1TB WD Blue HDD rm210
Tecware Titan Case rm259

Total RM4555

Yep, it's best to have SSD for windows. The one I draft there can be further fine tuned for OP purpose. I agree with you on 240GB ssd addition instead of 120GB. Swapping mobo and psu to cheaper ones will definitely get him a 250GB ssd. But 120GB is a no go for me as even 250GB is only having enough space for like 3-4 AAA games.