800AUD is approx. 633USD
adjusted for Australian market prices, excluding Shopping Express:
PCPartPicker part list:
https://au.pcpartpicker.com/list/XRdtm8
Price breakdown by merchant: https://au.pcpartpicker.com/list/XRdtm8/by_merchant/
CPU: AMD - Ryzen 3 1200 3.1GHz Quad-Core Processor ($139.00 @ Umart)
Motherboard: Asus - PRIME B350M-A Micro ATX AM4 Motherboard ($119.00 @ Mwave Australia)
Memory: G.Skill - NT Series 8GB (1 x 8GB) DDR4-2133 Memory ($110.00 @ IJK)
Storage: Seagate - Barracuda 2TB 3.5" 7200RPM Internal Hard Drive ($80.00 @ PLE Computers)
Video Card: Asus - GeForce GTX 1050 Ti 4GB Phoenix Video Card ($219.00 @ Centre Com)
Case: Silverstone - PS09B MicroATX Mid Tower Case ($45.00 @ Umart)
Power Supply: Corsair - Builder 500W 80+ Bronze Certified ATX Power Supply ($85.00 @ Scorptec)
Optical Drive: LG - GH24NSB0 DVD/CD Writer ($17.00 @ IJK)
Total: $814.00
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2018-01-13 12:49 AEDT+1100
i opted for a microATX motherboard with at least 4 ram slots, 6 sata ports, and a m.2 slot. It costs a few extra $$, but it lets you add things if necessary.
I excluded a ssd because of the price range. I suggest you buy one in the future.