Reddit mentions of Giga-byte Radeon 4GPcie3 4gb gddr5 1230mhz hdmi dp dvi ( GV-RX460WF2OC-4GD )

A budget would really help, however I will assume less than £500

Hard Drive: Just use the one you currently have. Rip it out of the old case and put it in the new one.

Case: https://www.amazon.co.uk/d/Computer-Cases/Bitfenix-Nova-Midi-Tower-Case-Window-BFX-NOV-100-KKWSK-RP/B016CMS1IW/ref=sr_1_1?ie=UTF8&qid=1483409986&sr=8-1&keywords=Case

RAM: Either use the sticks you currently have or go with my suggestion Link:https://www.amazon.co.uk/Ballistix-PC3-12800-240-Pin-Memory-BLS2CP4G3D1609DS1S00CEU/dp/B006YG94Y2/ref=sr_1_2?s=computers&ie=UTF8&qid=1483410182&sr=1-2&keywords=8GB+Ram

PSU:https://www.amazon.co.uk/Corsair-CP-9020097-UK-VS550-Power-Supply/dp/B00TE4XSMA/ref=sr_1_3?s=computers&ie=UTF8&qid=1483410222&sr=1-3&keywords=500W&th=1

Motherboard:https://www.amazon.co.uk/Gigabyte-Z97P-D3-LGA1150-Motherboard-USB3-0/dp/B00K9R1OCW/ref=pd_bxgy_147_img_2?_encoding=UTF8&psc=1&refRID=KG36WQ18GX84PCBY8N2K

CPU:https://www.amazon.co.uk/Intel-Cache-Graphics-Technology-Socket-x/dp/B00K5J2252/ref=sr_1_6?s=computers&ie=UTF8&qid=1483410268&sr=1-6&keywords=I5

Graphics card:https://www.amazon.co.uk/Gigabyte-OC-4Gb-GDDR5-Memory-Graphics/dp/B01JPAVZQI/ref=sr_1_2?s=computers&ie=UTF8&qid=1483410344&sr=1-2&keywords=RX+460

Hey dude so this appears to be the specs for your motherboard http://www.asrock.com/mb/AMD/FM2A68M-HD+/?cat=Specifications

It appears you should have two DDR3 Ram slots , I would assume based on your current RAM of 4GB that this is 2 x 2GB stick of RAM so to upgrade you would need 2 x 4GB sticks. I would recommend going to "http://uk.crucial.com" running their system scan which will recommend some RAM upgrades. If shipping is to expensive to Europe (I am assuming your in Europe :) ) try Amazon.

For a new Graphics card your motherboard supports PCE3.0 so something like this "https://www.amazon.co.uk/Gigabyte-OC-4Gb-GDDR5-Memory-Graphics/dp/B01JPAVZQI/ref=sr_1_1?s=computers&ie=UTF8&qid=1503413906&sr=1-1&keywords=RX+470"

Yeah. You could get it cheaper from amazon.

https://www.amazon.co.uk/dp/B01JPAVZQI/?tag=pcp0f-21

Overwatch uses 1-2 GB depending on the graphics settings. I couldn't find any info on Smite. You could get away with the 2GB version, but FPS will get reduced somewhat when the VRAM is close to maxing out. Gigabyte's 4GB version is only £15 more and would probably be worth it.