It does matter actually, more games are utilizing > 2GB now.

If not heavy usage or workload like rendering, getting overclockable rig won't benefit you much now since locked i5 speed is fast enough.

If you have budget then why not 

Get more RAM also if you render a lot, otherwise some software might use all your available 8GB RAM during rendering and your PC will slow down like a snail.

Since you are going for unlocked i5 + Z170, maybe you can go for locked i7 + H170/B150, it is cheaper or about the same price but you get extra 4 threads compared to i5.

Yes, GPU oc can be done with normal board.

What's your budget again? (Lazy to find because too many pages to look for  )

Intel Core i7 6700 - RM 1349
Gigabyte H170 Gaming 3 - RM 579
Corsair 16GB (8GB x 2) DDR4 2133MHz Value RAM - RM 400
Gigabyte GTX960 4GB GDDR5 Windforce OC - RM 1019
Kingston HyperX Fury 240GB SSD - RM 399
Seagate Barracuda 2TB HDD - RM 349
Seasonic M12II EVO 620W - RM 409
Bitfenix NOVA - RM 149

Total: RM 4653 (Techview price inclusive of GST)

Since the price of this GTX960 is over 1k, you can consider the R9 380/R9 380X 4GB, price is around the same but it is slightly faster than GTX960 in terms of raw performance. Or alternatively you can add RM 500 for MSI Tiger GTX970, almost twice the performance of GTX960.

GTX970 is more future proof, it is the hottest GPU right now for 1080p gaming.

If you don't plan to play any triple A titles now or in the future, GTX960 is enough for MMORPG (if I recall correctly you are playing online MMORPG right?) now.

If you plan to use GPU cooler i.e. Kraken G10 with AIO water cooler (not included in the G10), then just get the cheapest reference card because you will remove the default cooler of the GPU, so it is just a waste to buy those expensive aftermarket cooler equipped GPU.
Based on your frequently used/played games, it is enough unless you are planning to play latest triple A titles at high settings.

Intel Core i7 6700 - RM 1349
MSI B150M Bazooka D4 - RM 409
Corsair 16GB (8GB x 2) DDR4 2133MHz Value RAM - RM 400
Zotac GTX970 4GB GDDR5 ZT-90101-10P - RM 1479
Kingston HyperX Fury 120GB SSD - RM 229
Bitfenix NOVA - RM 149

Total: RM 4015 (Techview price inclusive of GST)

For 3.5k build, you can:
1. Remove SSD + 8GB RAM
2. Downgrade to i5 6500
Don't need aftermarket cooler so soon I think, Gigabyte Windforce does the cooling job pretty good, I am using the triple fan Windforce card, the temperature never hit > 70°C when no air cond, average 60°C when in air cond room.

You still can oc the GPU even with the stock cooler, but Gigabyte Windforce card comes with factory oc'd settings, so you don't really need to oc manually unless you really want to hit the max performance before the card throttles due to limit.

Where can I find the promotion??

thanks for SSD suggest but I don't really need it rn cuz all of my personal files are stored in External HDD (I have 2) that's why Im looking for motherboard with lots of USBs.

oh I forgot about one thing, since Im far far away from Modem(my room just a opposite site to another room cuz there's a another basic use Desktop) so should I buy wifi slot or USB wifi slot??

Yeah I know but 120GB isnt too small for me?
because right now I use around 250GB/750GB of HDD (I have some other games to play so)

what about the price? so I can recount the price again