Is your budget up to $1000 or would you prefer to spend less? You don't need very powerful hardware to play LoL and overwatch, those aren't very demanding games.
Cheap option:
PCPartPicker part list / Price breakdown by merchant
| Type | Item | Price |
|---|---|---|
| CPU | Intel Core i3-6100 3.7GHz Dual-Core Processor | $110.99 @ SuperBiiz |
| Motherboard | Gigabyte GA-H110M-A Micro ATX LGA1151 Motherboard | $53.88 @ OutletPC |
| Memory | Crucial 8GB (1 x 8GB) DDR4-2133 Memory | $26.99 @ SuperBiiz |
| Storage | Kingston SSDNow V300 Series 120GB 2.5" Solid State Drive | $41.33 @ OutletPC |
| Storage | Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive | $47.49 @ OutletPC |
| Video Card | EVGA GeForce GTX 950 2GB Superclocked Video Card | $129.99 @ NCIX US |
| Case | Deepcool TESSERACT SW ATX Mid Tower Case | $38.99 @ SuperBiiz |
| Power Supply | Corsair CX 500W 80+ Bronze Certified Semi-Modular ATX Power Supply | $37.98 @ Newegg |
| Prices include shipping, taxes, rebates, and discounts | ||
| Total (before mail-in rebates) | $527.64 | |
| Mail-in rebates | -$40.00 | |
| Total | $487.64 | |
| Generated by PCPartPicker 2016-05-30 04:52 EDT-0400 |
Slightly less cheap option:
PCPartPicker part list / Price breakdown by merchant
| Type | Item | Price |
|---|---|---|
| CPU | Intel Core i5-6500 3.2GHz Quad-Core Processor | $194.99 @ SuperBiiz |
| Motherboard | Gigabyte GA-H110M-A Micro ATX LGA1151 Motherboard | $53.88 @ OutletPC |
| Memory | Corsair Vengeance LPX 16GB (2 x 8GB) DDR4-2400 Memory | $57.99 @ Newegg |
| Storage | Kingston SSDNow V300 Series 120GB 2.5" Solid State Drive | $41.33 @ OutletPC |
| Storage | Western Digital Caviar Blue 1TB 3.5" 7200RPM Internal Hard Drive | $47.49 @ OutletPC |
| Video Card | Sapphire Radeon R9 380 4GB NITRO Dual-X OC Video Card | $179.99 @ Newegg |
| Case | Deepcool TESSERACT SW ATX Mid Tower Case | $38.99 @ SuperBiiz |
| Power Supply | Corsair CX 500W 80+ Bronze Certified Semi-Modular ATX Power Supply | $37.98 @ Newegg |
| Prices include shipping, taxes, rebates, and discounts | ||
| Total (before mail-in rebates) | $687.64 | |
| Mail-in rebates | -$35.00 | |
| Total | $652.64 | |
| Generated by PCPartPicker 2016-05-30 04:53 EDT-0400 |
The case doesn't really matter, just pick out one that you like and that you can afford. Doesn't have to be a corsair PSU either, but avoid cheap brands. Stick to EVGA/coolermaster/corsair/antec/seasonic.