Ok, so if I understand correctly, you don't need to do any video editing. In which case you wouldn't need a dedicated GPU and can potentially save money tto get a better CPU and more RAM, which is what you really need here.
PCPartPicker part list /
Price breakdown by merchant
CPU: AMD - Ryzen 5 2400G 3.6GHz Quad-Core Processor ($158.89 @ OutletPC)
Motherboard: ASRock - B450M PRO4 Micro ATX AM4 Motherboard ($79.99 @ Newegg)
Memory: G.Skill - Ripjaws V Series 32GB (4 x 8GB) DDR4-3200 Memory ($283.99 @ Newegg)
Storage: Samsung - 860 Evo 500GB 2.5" Solid State Drive ($87.99 @ Amazon)
Storage: Seagate - Barracuda 2TB 3.5" 7200RPM Internal Hard Drive ($58.89 @ OutletPC)
Case: Fractal Design - Define Mini C MicroATX Mid Tower Case ($75.87 @ Newegg Business)
Power Supply: EVGA - 450W 80+ Bronze Certified ATX Power Supply ($59.89 @ OutletPC)
Total: $805.51
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2018-09-30 14:51 EDT-0400
Have a look at this build. The CPU I chose if the Ryzen 5 2200G, which is very good for photo editing. It also has integrated graphics, which more than what you'll ever need for photo editing. I went with a slightly more expensive case at 75$ because first of all it has dust filters all over, which is something you definitely want but it also has A LOT of drive-cadies as you will add more storage over time.
You could potentially go for a stronger CPU like the Ryzen 7 models, with a NVIDIA Quadro Graphics card if you're planing to do video editing in the future, but you will need to cut back on RAM to fit your budget so I wouldn't recommend it.
I own a Digital Marketing Startup with a small team so I am suggesting you the build I wish I could have gotten but I'm lacking the budget so I went with the Ryzen 3 2200g and only 16Gb of RAM.
As for monitors, I personally use the LG 24" Neo Blade III at home, which is fantastic. At the office, I went for something more budget friendly: HP N240.
In theory you need to go for a IPS-Type panel. These displays have better contrast, colour range, brightness and viewing angles. TN Panels will be cheaper and you will probably be able to find 4K TN panels at similar prices to 1080p IPS displays, but I would even recommend a 1080p IPS display instead as you can just zoom in to be more precise in Photoshop and all.
Note that these 2 I used are 1080p monitors. If you want to edit in 4k, you will need a dedicated graphics card that can support this, so I would suggest this next build instead.
PCPartPicker part list /
Price breakdown by merchant
CPU: AMD - Ryzen 5 2600 3.4GHz 6-Core Processor ($165.99 @ Amazon)
Motherboard: ASRock - B450M PRO4 Micro ATX AM4 Motherboard ($79.99 @ Newegg)
Memory: G.Skill - Ripjaws V Series 32GB (4 x 8GB) DDR4-3200 Memory ($283.99 @ Newegg)
Storage: Samsung - 860 Evo 500GB 2.5" Solid State Drive ($87.99 @ Amazon)
Storage: Seagate - Barracuda 2TB 3.5" 7200RPM Internal Hard Drive ($58.89 @ OutletPC)
Video Card: PNY - Quadro K620 2GB Video Card ($159.99 @ Dell)
Case: Fractal Design - Define Mini C MicroATX Mid Tower Case ($75.87 @ Newegg Business)
Power Supply: EVGA - 500W 80+ Bronze Certified ATX Power Supply ($39.89 @ OutletPC)
Total: $952.60
Prices include shipping, taxes, and discounts when available
Generated by PCPartPicker 2018-09-30 14:50 EDT-0400